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Johannes Kepler's on the More Certain Fundamentals of Astrology Prague 1601
Author(s): J. Bruce Brackenridge and Mary Ann Rossi
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Source: Proceedings of the American Philosophical Society, Vol. 123, No. 2 (Apr. 27, 1979), pp.
85-116
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JOHANNES KEPLER'S
ON THE MORE CERTAIN FUNDAMENTALS OF ASTROLOGY
PRAGUE
1601
FOREWORD, NOTES, AND ANALYTICAL OUTLINE BY
J. BRUCEBRACKENRIDGE
NEWLY TRANSLATED FROM THE LATIN BY
MARYANN ROSSI
FOREWORD
The ScientificBasis of Astrology
The traditional textbook in physics or astronomy
views Johannes Kepler only with regard to his contributions to astronomy and, in particular, with regard to that limited portion of his astronomical works
that has proved to be of continued utility: his three
laws of planetary motion. If his astrological views
are discussed at all, it is assumed that as an enlightened
astronomer he believed astrology to be nonsense or at
best a source of income forced on him by an unenlightened patron. Such a view is not supported either
by Kepler's writings or by the tradition of scientific
astrology in which he worked. This tradition has
roots that extend back to the earliest recorded scientific
endeavors. In fact, Otto Neugebauer in his Exact
Sciences in Antiquity makes a strong case for the claim
that initially the fundamental doctrines of astrology
were pure science.
to his great work on astrology, the Tetrabiblos, the
astronomer Ptolemy clearly makes the distinction between the two disciplines: on the one hand, astronomy
is concerned with observing, recording, and predicting
the juxtapositions (aspects) of the celestial bodies
with great scientific precision; on the other hand,
astrology is concerned with applying the knowledge
of the astronomical aspects to the less exact and more
mundane task of predicting terrestrial events. Nevertheless, both disciplines have in common a concern
with the heavens, and both have a rational basis for
their operation. Ptolemy states:
Of the means of prediction through [celestial observations] . . . two are the most importantand valid. One,
which is first both in order and in effectiveness is that
whereby we apprehendthe aspects of the movements of
sun, moon, and stars in relation to each other and to the
earth, as they occur from time to time [i.e., astronomy];
the second is that in which by means of the natural
character of these aspects themselves we investigate the
changes which they bring about in that which they
surround [i.e., astrology]. The first of these . . . has
been expounded to you as best we could in its own
treatise (the Almagest) by the method of demonstration.
We shall now give an account of the second and less
sufficientmethod in a properlyphilosophicalway, so that
the one whose aim is the truth might never compare its
perceptions with the sureness of the first, unvarying
science, for he ascribesto it [astrology] the weaknessand
unpredictabilityof material qualities found in individual
things nor yet refrain from such investigationas is within
the bounds of possibility, when it is so evident that most
events of a general nature draw their causes from the
enveloping heavens.2
To a modern scientist, an ancient astrological treatise
appearsas mere nonsense. But we shouldnot forget that
we must evaluatesuch doctrinesagainst the contemporary
background. To Greek philosophersand astronomersthe
universe was a well defined structure of directly related
bodies. The conceptof predictableinfluencebetweenthese
bodiesis in principlenot at all different from any modern
mechanistictheory. And it stands in sharpestcontrastto
the ideas either of arbitrary rulership of deities or of
the possibilityof influencingevents by magical operations.
Comparedwith the backgroundof religion, magic, and
mysticism, the fundamentaldoctrines of astrology are
pure science. Of course, the boundariesbetween rational
science and loose speculation were rapidly obliterated
and astrologicallore did not stem-but ratherpromotedsuperstition and magical practices.'
This astrological boundary between rational science
Ptolemy continues by saying that although "alleand loose speculation has been patrolled and defended gations against the first can only be made by the
by two outstanding astronomers: Claudius Ptolemy in blind" and that "there are spacious grounds for those
the second century A.D., and Johannes Kepler in the leveled at the second," nevertheless he intends to
seventeenth century A.D. Both these men see a purity examine "the measure of both the possibility and
in astronomy that does not exist in astrology, but the usefulness of such prognostication." After all, he
fundamentals of astrology, nevertheless, are defended reminds us, "everything that is hard to obtain is
as being well founded in science. In the introduction easily assailed."
PROCEEDINGS OF THE AMERICAN
PHILOSOPHICAL
SOCIETY, VOL.
123,
85
NO.
2,
APRIL
1979
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BRUCE BRACKENRIDGE
Astrology is concerned with events in the world of
flux that exists below the lunar sphere while astronomy is concerned with events in the universe of perfection that exists beyond the lunar sphere. For
Ptolemy, as for Aristotle, these are two separate and
distinct entities. Nevertheless, there is a link between
them. Aristotle, in On Comning into Being and
Passing Away, gives the approach and recession of
the sun as the formal cause for the origin of all movement, generation, and corruption on earth. Ptolemy
also begins his defense of the link between celestial
and terrestrial events by considering the obvious influence of the sun (ask any farmer) and of the moon
(ask any sailor). Further, the stars can predict important meteorological phenomena (each year when
the dog star Sirius rises with the sun, the Nile floods).
And then he addresses the more complex but equally
important question of aspects or juxtapositions of the
planets. Unlike astronomy with its ability to make
precise predictions of celestial events, there are limits
to the ability of astrology to make accurate predictions
of terrestrial events. But Ptolemy says, "It would
not be fitting to dismiss all prognostications of this
character because it can sometimes be mistaken, for
we do not discredit the art of the pilot for its many
errors."
Although Newton did not believe gravity to be an
"innate, essential and inherent property of matter,"
nevertheless for eighteenth-century "Newtonians"
gravitation and mathematical physics combined to
offer the ultimate and final explanations for all the
subtleties of celestial motion that the astronomer could
observe. At the end of the eighteenth century the goal
of LaPlace's great work on astronomy was "to reduce
all the known phenomena of the system of the world to
the law of gravity, by strict mathematical principles,
and to complete the investigations of the motions of
planets, satellites, and comets, begun by Newton in
his Principia." 3 He appeared to accomplish this task.
There was, however, no successful application of gravitational theory to astrology. The gravitational influence of planets on terrestrial objects was too weak
and too complex to lend itself to the type of mathematical analysis that proved so successful for astronomy. The two disciplines now clearly must go their
separate ways.
But neither Ptolemy in the second century nor
Kepler in the seventeenth century had to grapple with
the mysticism of that occult force, gravitation. The
origin of the tradition in which Ptolemy operated can
be traced back to Plato. In the sixth century A.D.
commentary on astronomy, Simplicius formulated the
Platonic tradition of the fourth century B.C. as follows:
Plato lays down the principle that the heavenly bodies'
motionis circular,uniform,and constantlyregular. Thereupon he sets the mathematiciansthe following problem:
What circularmotions, uniformand perfectly regular are
[PROC. AMER. PHIL. SOC.
to be admittedas hypothesesso that it might be possible
to save the appearancespresented by the planets?4
The first response to this charge was by Plato's contemporary Eudoxus, who proposed a nest of twentysix homocentric spheres: one sphere for the motion of
the stars, two spheres for the sun, three for the moon,
and four for the five planets. Aristotle objected to
this system on the ground that, as a mathematical
formulation, it served only as a calculating device. He
sought a system that represented in physical fact the
mechanism of celestial motion. In such a physical
system the motions of each set of spheres would interact with each of the other sets, and additional spheres
would be required to "roll back" the motion of those
spheres preceding it. This mechanical system of
nested spheres requires fifty-five spheres in all.
Whatever homocentric system was elected, it was
in effect a combination of circular motions, all centered
about the earth. The next major refinement in technical astronomy was the introduction of the epicycle
by Hipparchus in the second century B.C. In an
epicycle a planet revolves in a circle whose center is
a point in space; this point itself revolves in a circle
whose center is the earth. If the periods of the two
motions, that of the planetary circle called the epicycle
and that of the center of the epicycle called the deferent,
are equal and opposite, the result is simply motion on a
simple circle eccentric to the earth. If the periods are
not the same, more complex motions can be obtained.
Ptolemy, in the second century A.D., carried this
technical, mathematicalanalysis of circular motion to its
fruition by combining eccentric and epicyclic motions
and by adding yet a third variation, the equant; this
device controls the speed of the center of the epicycle
on the deferent by making it uniform but with respect
to yet a third point, which is neither the earth nor the
center of the deferent. The system does violence to
Plato's charge of uniform motion, at least with respect
to the earth, but it continues in the tradition of perfect celestial circularity. Further, though it is complicated, nevertheless it is capable of saving the phenomena. Not until Kepler's New Astronomy was
published in 1609 could any system compare to it.
The popular belief that Copernicus'heliocentric system
constitutes a significant simplificationof the Ptolemaic
system is obviously wrong. The choice of the reference
system has no effect whatever on the structure of the
model, and the Copernican models themselves require
about twice as many circles as Ptolemaicmodels and are
far less elegant and adaptable. In fact, the importance
of Copernicus'work lies in a totally different direction
than generally announced.5
What is important for us to note is that neither
Ptolemy nor Copernicus makes any reference to what
may be called the "physical causes." It is in the
nature of a celestial object, such as a planet, to move
in a circle, just as it is in the nature of a terrestrial
VOL. 123, NO. 2, 1979]
KEPLER ON ASTROLOGY
object, such as a falling stone, to move in a rectilinear
fashion toward its "natural place." Since such a natural and geometric explanation is sufficient for astronomical phenomena, it is equally natural, and thus
equally scientific, for geometry to explain astrological
phenomena. Given the astrological powers of the
luminaries and planets from their juxtaposition (see
Note 18), the nature and order of the constellations in
the Zodiac from tradition, and the motions and juxtapositions of the planets from astronomy, Ptolemy may
make some logical and scientific attempt to predict the
"established influence" of celestial bodies on terrestrial
events.
By the beginning of the seventeeth century, however, the situation was changed. Copernicus' work,
despite having been forced into complex Ptolemaic-like
convolutions in order to predict detailed planetary motions, suggested certain overall simplifications. Moreover, the great Danish practical astronomer, Tycho
Brahe, had amassed celestial data far superior to
Ptolemy's (2" of arc contrasted to Ptolemy's 10").
Finally, the English physician William Gilbert had
written a book, On Magnets, in which he discussed the
earth's magnetic efflux and analyzed its ability to
attract and repel lodestones. All three authors are
mentioned in Kepler's great survey and review of his
work The Epitome: "I build my whole astronomy
upon Copernicus' hypotheses concerning the world,
upon the observations of Tycho Brahe, and lastly upon
the Englishman William Gilbert's philosophy of magnetism." 6
It is understandable that he would heed the work of
Copernicus and Tycho, but of what interest is terrestrial magnetism in a work devoted to celestial
motion? Even though Copernicus had attempted to
shift the center of celestial circular motion, nevertheless he maintained the Platonic and Aristotelian tradition of natural celestial circularity. Celestial bodies
move as they move because it is in their nature to
move that way. A careful analysis of Tycho's data
for Mars forced Kepler to break with the tradition of
planetary circles and to replace them with ellipses.
But of equal interest is Kepler's concern with "physical
causes." He recognizes that there are irregularities in
the paths of planets (i.e., they do not move uniformly
in circles, but rather the radius varies in distance as
prescribed by the law of elliptical paths, and the
speed varies as prescribed by the law of equal areas
in equal times); he accordingly describes a physical
mechanism by which the supposed magnetic efflux of
the rotating sun sweeps the planets around in their
orbits. Further, since Kepler's sun is essentially a
magnetic monopole and the planet a magnetic dipole
of fixed inclination, he can account for variations in
the radius of the path because the planet is attracted
or repulsed as it changes its relative magnetic orientation with respect to the sun. It is not important here,
87
however, to understand or to evaluate the mechanisms;
what is important to note is Kepler's feeling that he
should attempt such a physical analysis.
Before one makes an eighteenth century Newtonian
of Kepler, however, it is well to consider his devotion
to the other and more traditional causes in astronomy:
the geometric tradition that had to this time served the
astronomer so well. Certainly in his earlier work
The Cosmographic Mystery (see Note 29) and in his
later work The Harmonies of the World (see Note
30) he sings the praises of God and Geometer and of
the mysteries and order revealed through this means
alone. Even in the Epitome itself the supremacy of
geometrical causes can be found:
Then you evaluate the density of the lunar body as proportioned to twelve lunar revolutions in one year: what
will you say is the archetypalcause of this number?
The cause seems to be compositeof geometricalbeautyand
of the office of this planet in the world as follows: For
the moon is a secondary planet assigned to the Earth,
and it keeps to its own private course around the Earth.
But 360 revolutionswere allotted to the Earth, while the
centre of the Earth makes one return around the sun.
Then, just as among the upper planets, the sphere of the
moon had to be a mean proportionalbetween the body of
the Earth and the sphere wherein the centre of the Earth
really revolves,but the sun apparently;so also the revolutions of the moon had to be more than one but fewer
than 360. And indeed the mean proportionalbetween
1 and 361 is 19; but because the number 361 is not 360
and because 19 does not have any beauty either geometrical or harmonical; then the two numbers nearest
to 19, which when multipliedtogether, give 360 and are
the most beautifulgeometricallyand harmonically,should
be chosen. Now the nearest numbers which give 360
are 18 and 20, becausethe first is smallerby unity alone,
and the second greater than 19 by unity alone. But
there is no demonstrationof a figure of 18 sides. The
numbersfollowing nearest are 15 and 24, which also give
360. Now there are geometricaldemonstrationsof them,
but ratherworthlessones; nor do they give any outstanding ratio, but only the ratio between5 and 8; nor are they
the most excellent and first of all in harmonics. But the
numbers12 and 30-for there are no others nearer which
give 360-excel in all ways; both geometrically,as being
generated from the first figures inscribed in the circle,
and harmonically,because all harmonies are represented
by these two divisions of the string. Then of the numbers
which, when multipliedtogether,give 360, there are none
more beautiful.7
It is with this mixed background of physical and
geometrical explanations of astronomical causes that
Kepler approaches his analysis of astrology. In the
best tradition of Ptolemy he seeks to protect its borders
from those who, in Neugebauer's words, would
obliterate "the boundaries between rational science
and loose speculation." Kepler's title On the More
Certain Fundamentals of Astrology attests to this
concern and illustrates his belief that such fundamentals exist. The modern astronomer associates
astrology with magic and mysticism, while accepting
astronomy as a science. Kepler, however, like
88
BRUCE BRACKENRIDGE
Ptolemy, views astrology as the profane, utilitarian,
and less exact facet of that same activity of which
astronomy is the sacred, abstract, and exact science.
Unlike the modern astronomer, it was natural for Kepler to take astrology seriously.
Consequently he was concerned in this work to set
forth clearly both the possibilities of astrology and its
limitations. Before making the actual predictions for
the year 1602, he introduces the more certain fundamentals of the science. The first to be discussed,
though not necessarily the most important, are the
physical causes, much in the same fashion as they are
introduced into his astronomical works. The sources
of the physical causes are the sun, the moon, and the
planets; and the physical mechanism is the light that
comes down from each. The traditional astrological
powers of each planet must be retained (i.e., Mars is
hot and dry as evidenced by its history of successful
astrological usage), but the reasons for such powers
must be revised. Previously the powers arose from
the juxtaposition of the planet to the sun and the
moon; now, with Kepler's adoption of the Copernican
system, these juxtapositions have changed (see Note
18). The powers are derived instead from a consideration of the optical properties of each planet.
The discussion of the physical causes is followed in
Thesis 36 by "another cause, which pertains equally
to all planets, nobler by far than those mentioned earlier, and one possessing far more wonder." This is
the geometric cause, whose source lies chiefly in the
traditional five aspects of astrology augmented by the
three new aspects suggested by Kepler (see Note 31).
The receptor of such influences is an animate faculty,
which is likened to a fourth type of soul (see Note 32).
But not all of the traditional geometric causes of
astronomy are accepted. The signs of the Zodiac are
treated with contempt. In Thesis 49 Kepler states,
"But nothing is more intolerable in this almost unique
concern of astrologers than that they distribute with a
certain infantile credulity twelve houses among seven
planets beyond every sound and philosophical reason."
The predictions that follow comprise a month by
month forecast of the weather for the year 1602 (in
the best tradition of the Farmer's Almanac). When
questions concerning predictions of crops are posed,
he replies in Thesis 65: "The stuff of empty dreams
are those divisions assigned by astrologers to grain,
oil, corn, etc., according to the dispositions of the
cardinal configuration of Jupiter. Do you want to
know why wine has not turned out well this year?
Because the year has been cold and humid. Whoever
has made this observation has understood the effect
from this cause alone."
The work concludes with a discussion of four major
aspects of special significance in 1602, and with an
invitation to all who think his fundamentals worthy
[PROC. AMER. PHIL. SOC.
of consideration, to join with him in a discussion in
order that the truth may be discovered.
It is tempting to see Kepler and his three laws of
planetary motion in the guise of modern astronomy.
In the final analysis, however, Kepler remains a man
of his own time. His approach to astrology is changing in the same way that his approach to astronomy
is changing. But by no means does he reject the
science of astrology as does a modern astronomer.
As Gerard Simon puts it:
We see clearly here what, with Kepler, is changing in
western culture although he was not in a position to
state it explicitly: the possibility of describing a causal
process has become the criterion of rationality,and outside it there is no intellectualsalvation. When he undertook to make astrology healthy, he thus imposed the
modern demand of causal determinismon archaic conceptions which had grown out of the demandsof a quite
differentkind of reasoning. The remedywas clearly one
of those which in the end will kill the patient.8
For Kepler, there was no need to discard astrology.
Quite the contrary, what was needed was a clear
formulation of the foundations of astrology; of these
he was certain.
TRANSLATOR'SPREFACE
My training is in the classical languages and civilization while that of my husband, Bruce Brackenridge,
was initially in classical physics and more recently
has been in the history of science. Since I know
very little astronomy and he knows very little Latin,
this translation was done in the best "Jack Spratt"
tradition. I would offer the possible English translations that a section would allow and he would select
that which made the best physical sense or would suggest compromises that would send me back to the
Latin for a reappraisal. It was my charge to defend
the dignity of the Latin and his to defend the integrity
of Kepler.
We began this hybrid venture in London early in
1975 when I was a Reader in Classical Studies at
Birkbeck College in the University of London and
teaching Greek, Latin, and Renaissance Latin in the
City Literary Institute. At the same time he was an
academic visitor in the Department of History of
Science at Imperial College in the University of London and teaching at the London branch of Lawrence
University. The motivation for beginning the translation was a course in astronomy and astrology that
my husband was scheduled to teach. The English
translation of the Tetrabiblos, the astrological companion for Ptolemy's astronomical work, the Almagest,
was readily available in the Loeb edition. The equivalent astrological work of Kepler, On The More Certain
Fundamentals of Astrology, had been translated into
English, and had been published in 1942 by Clancy
Publications of New York, but it had long been out
KEPLER ON ASTROLOGY
VOL. 123, NO. 2, 1979]
of print and, in fact, a search of five of the major
libraries of London failed to produce a copy. Thus,
with the invaluable aid of one colleague and with the
encouragement of others, the task was begun early in
the spring, and the first draft was completed by midsummer of 1975 for use by the students in London
during the summer term.
Upon our return to Appleton, Wisconsin, this translation was again used in a class during the spring term
of 1976. During this term, we also obtained a copy
of the New York translation that was published in
1942. We found that the latter was lacking a translation of the dedication and adequate explanatory
notes. More important, we thought that the English
rendition was unsatisfactory because at times it was
inaccurate in its translation and often incorrect in its
interpretation. Moreover, after two classroom experiences with the original London translation, we
found that it was also subject to some of the same
criticisms that we had leveled at the New York translation. Thus, in the summer of 1976, we decided, with
the aid of the two translations now in our possession,
to try once again. The result is this translation,
which we shall call the Appleton edition.
The major source, of course, is the original Latin
edition, published by Kepler in Prague late in the
year, 1601. It was only one of the many major pub-
89
lications of Kepler, the first being the Cosmographic
Mystery in 1596 and the last being the Rudolphine
Tables in 1630, the year of his death. In the interim
he wrote twenty other major works, generally in
Latin, but sometimes in German. These original
works are now quite rare and often difficult to obtain,
but fortunately two editions of the collected works
have been printed. The first 9 was published in the
nineteenth century and has recently been reprinted.
The second,10 the one used for this translation, was
begun early in the twentieth century (1938). Bibliographical references both to the original works and
to the English translations may be found in an English
translation of the German biography of Kepler by
Max Casper 1 and in a biographical article on Kepler
by Owen Gingerich.12
In this translation I have used brackets [] to
indicate words added for explanation or clarification;
the capitalization, punctuation, and paragraphing have
been accommodated to modern usage. We have added
an analytical outline that divides the work into three
major sections, each with subsections and explanatory
headings. There is indeed a risk in imposing such a
structure, but it may provide an aid to the person who
reads the work for the first time.
We commend this little work to your reading and
hope that it brings some measure of joy to you.
ON THE MORE CERTAIN FUNDAMENTALS OF ASTROLOGY
A NEW BRIEF DISSERTATION REGARDING COSMIC THEORY
WITH A PHYSICAL PROGNOSIS OF THE COMING YEAR 1602 A.D.
WRITTEN FOR PHILOSOPHERS
by
M. JOHANNES KEPLER
Mathematician
Men, tell the power of the heavens; the known may be put to our profit;
While in a field unexplored,you can see no gain or profit.
Labor resides in defeat, whereas victory will benefit richly,
Nature's power do reveal, O Mankind, by your wit.
at Prague,
Schuma
TO MY MOST ILLUSTRIOUS MASTER, LORD
PETRUS WOK DE ROSENBERGK, IN KRUMLOV,
BOHEMIA AND TO THE MASTER OF THE NOT
UNRENOWNED HOUSE OF THE ROSENBERGKS,
THE COUNSELOR OF HIS HOLY AND IMPERIAL
MAJESTY, MY LORD CLEMENT:
ANALYTICAL OUTLINE
Title Page
Dedication
Thesis
Introduction.....................
..............
Section One: On Physical Causes.........................
A. The Sun........................................
1. The time of elevation...........................
2. The nature of the atmosphere .................
1, 2, 3
4
5
6
7, 8
3. The obliquity of the sun's rays ...................
9
4. The numericalevaluation ...................
10, 11
5. The heat capacity of the earth............
12, 13, 14
B. The Moon.............................15,
16, 17, 18
C. The Planets...................
..................
19
1. The faculties of light ........................20,
21
22
2. The combinationsof faculties....................
3. The combinationsassigned to planets .........23,
24
4. The physical cause of planetary differences........25
a. Reflected light ........................26,
27, 28
b. Radiated light ...........................29,
30
5. The applicationof planetarypropertiesto
the making of predictions..............31,
32, 33, 34
D. A Summary of the Physical Causes.................35
Section Two: On GeometricalCauses .................36,
37
A. Aspects .........
...............................38
1. The Animate Faculty introduced....... 39, 40, 41, 42
2. The Animate Faculty discussed by analogy........ 43
90
BRUCE BRACKENRIDGE
3. Individual planetary influenceson aspects.........44
B. Cycles....................................45,
46, 47
C. Harmonic Motions of the Planets...................48
D. Other ConjecturedCauses.
.............
49, 50, 51
Section Three: On Predictions for 1602.....................
A. The Weather for the Year 1602 .................
52-62
B. On Eclipses...................................63,
64
C. On Crops.........
66
...........................65,
D. On Illness ......................................67
E. On Political and Military Matters ..............68,
69
F. On Earthquakes..................................70
G. On Four Major Aspects of Special Significance
in 1603............................
71, 72, 73, 74, 75
Conclusion
In Book I of his work On Duties, Cicero points out
very clearly: "It is the mark of a great mind, and
there have been many, even in a rather busy life,
either to investigate or to try to investigate certain
great questions, and to hold themselves within the
bounds of their own fields." Applying this opinion
of Cicero's especially to the study of astronomy, our
Reinhold urges honest intellects not to allow themselves to be deterred from the study of astronomy
by the judgments of those unlearned people who admire only profitable skills. For, since these are studies
of virtue, one requires fortitude in cultivating them,
and this fortitude makes minds resolute against the
foolish opinions of the crowd and scorns false judgments.
What this excellent man has said about each part
of astrology, I thought that I might set forth at this
time especially from another standpoint, that of
p'hysics. People who write prognostics as a service
ought to despise, especially in their inmost heart, two
conflicting inclinations of the crowd and ought to
fortify themselves against two characteristics of a shallow and contemptible mind: desire for glory, and fear.
For, although popular demand [for prognostics] is
great, it is the mark of a corrupt mind in order to
curry the favor of the crowd or for vainglory either
to profess those things that nature does not exhibit, or
to conceal the genuine miracles of nature, if one does
not consider the more serious causes.
On the other hand are those who say that it is
not fitting for a serious and philosophical person to
prostitute the reputation of one's talents and the
honor of one's erudition in matters debased by the
very trivial and very empty daily soothsayings; by
furnishing this divining, one feeds the curiosity of
the crowd and kindles the superstitions of weak dispositions as if with a tinder. I confess that these
objections are put forward with great cogency and
that they are sufficient to deter the honest person, if
there are not more serious reasons, from this kind of
writing.
But if the desire to enlighten himself suffices as a
person's motive (and such motives are approved for
their own sake by wise men), then he cannot be
stopped, unless in his timid concern about rumors and
[PROC. AMER. PHIL. SOC.
in his fear of a bad reputation, he allows himself to be
deterred from his purpose by these outside influences
and approaching obstacles. For even if a great number of precepts are taken up with the trifles of the
Arabs in this field, still those things that are in this
hidden art of nature are not on that account trifles,
nor should they be rejected as trifles.
But gems must be gathered from the mire; the
honor of God must be set off by the proposed contemplation of nature, others must be attracted by
example; and we must turn our attention and bend
every effort to bring to light from the shadows of
ignorance those matters that once served as a distinct
advantage to the human race. And even if the outcome does not appear clear immediately and there
is great uncertainty in the predictions because of the
complexity of so many causes, nevertheless, one must
strive all the more, since in work alone may virtue be
observed.
As to the fact that many indeed abuse these [predictions] for their own curiosity, and confirm their
own superstitions, I am not deterred any more by
this than a good commander is deterred from attacking a city (and I pass over innumerable examples)
by the loss of a few soldiers (whom, if one could,
one would surely want saved).
If people have reservations about the publication of
astrological matters for the general public, in whom
there is slight hope of fruition, I should like them to
consider that we may not reach the learned lying
hidden here and there by any other means than a
public one.
Add to this that here the same method may be
observed in cultivating the curiosity of the crowd that
is observed by doctors in regard to a sick person, so
that we exploit the inordinate and pernicious desires
of the crowd in order to administer warnings (as if
some medication), veiled in the guise of prognostications, which serve to cure the disease of the mind,
warnings of such a kind that we could hardly administer them in any other way. Therefore, just as
doctors dealing with a sick person are not mad because they fall in with a delirious invalid by disguising the voice and falsifying appearances in order to
administer medicines, just so do I hope that those
listening to me in good faith will suspect nothing
sinister, because it is with the best intentions that I
speak openly about the future to the crowd, who are
eager to learn of new and future events. Those
judgments are unfair that ridicule and never pursue
the question of the greatest worth; in order not to
leave these rather lowly services of life neglected and
open to ridicule, take up [this book], so that, as he
[Cicero] has enjoined, I may rescue the mentally
blind.
Most illustrious Lord, I especially wished to dedicate to Your Highness as a New Year's gift, these
KEPLER ON ASTROLOGY
VOL. 123, NO. 2, 1979]
91
meditations of mine about the coming year, because I mechanismby which they exert their influence: reflected
am convinced that Your Highness and all learned per- light humidifiesand radiatedlight heats.]
sons have been disposed to look with favor upon the
Thesis 3
cultivators of these arts in particular, which you have
And indeed, as the cause, so is the effect. Truly
clearly shown by your words and especially by taking astrologers consider as causes of their predictions, to
into your friendship that most renowned man of great be
sure, some that are physical, and some that are
nobility, Tycho Brahe, phoenix of astronomers. Then political, but when they yield the pen to enthusiasm,
at his death, this [friendship] was offered to me as
[they consider causes that are] in greater part inadewell with a declaration of your sorrow at his loss.
quate, for the most part imaginary, foolish, and false,
And further you daily give evidence of your interest, and
finally altogether worthless. If they sometimes
since you entertain in your court that very famous
speak the truth when they are carried away by their
man, D. Hermann Bulder, Doctor of Medicine, a enthusiasm, it
ought to be marked up to good luck,
very dedicated mathematician and a very learned man and it must not be thought that it issues, more often
in this field; and you engage this gentleman in daily and for
the most part, from some higher and occult
discussions about these matters.
instinct.
Accept, then, most Illustrious Lord, these physical
Thesis 4
conjectures, and compare them with those political
I
refer
to
which
Some physical causes are known by everyone,
conjectures (which
very frequently),
the dignity of your rank and your concern for the others, by very few; moreover, many things indeed
State will furnish. For only those who deal with exist naturally, but from causes comprehended by no
the public interest will judge most accurately the fate one to this day. And of the causes that we consider
of this prognosis; professors of Philosophy will to be known, there are some whose kind and explanasurely lay claim to the philosophical and physical tion we all understand in common; there are others
paradoxes for their own use and for their own criti- whose kind, or related causes, either very few undercism.
stand, or no one at all.
Farewell. May you enjoy a long and pleasant old
A. THE SUN [The physical function of the sun is
age, and may you have a very Happy New Year. to heat. Its effectiveness
is influencedby three factors:
May Your Highness regard me as committed to your the time of elevation, the nature of the atmosphere,and
service.
the angle at which the sun's rays strike the horizon. FurM. JOH. KEPLER ther, one must consider the heat capacity of the earth
Mathematician itself.]
Thesis 5
INTRODUCTION
Thesis 1
It is commonly considered the duty of the mathematician to write annual prognostics. Since, therefore, I have decided to fulfill this obligation for the
coming year 1602 from the birth of Christ Savior by
confining them [the prognostics] not so much to the
curiosity of the public as to the duty of the philosopher, I shall begin with the principal prognostic
that can be cited with the utmost safety: that this
year there will be. a rich harvest of prognostics, since,
owing to increasing popular demand, more authors
are adding daily to their number.
The most general, most powerful, and most certain
cause, which is known to everyone, is that of the approach and withdrawal of the sun. This [cause],
then, brings about the winter solstice around the
birthday of Christ, the 21st of December, a bit before
6:00
P.M., and the summer solstice on the 21st of
June at 10:30 at night. The former will then be
[the cause of] the winter cold, and the latter, [the
cause of] the summer heat.
[1. The time of elevation.]
Thesis 6
The working of this cause is evident from the folThesis 2
lowing facts. At Prague, Bohemia, the altitude of the
In those pamphlets some matters will be foretold pole is 50o5'45". Now the inclination of the ecliptic
which the event will make credible; but many more in this century is 23?31'30", as observed by Tycho
will be foretold which time and experience will refute Brahe, that phoenix of astronomers, whom we have
as false and worthless. The latter will be written on recently lost. Thus the sun, the source of our heat,
the winds, the former very deeply inscribed in the shines in winter not more than 7 hours and 49 minutes
above the horizon, and so it heats our air for a brief
memory, as is the way of the world.
time, but lying more completely hidden below the
SECTION ONE: ON PHYSICAL CAUSES
horizon, it stops giving heat for [about] twice the
[There are three major sources of physical causes: the time. On the other hand in the summer, the sun
sun, the moon, and the planets. Light is the primary remains for 16 hours and 22 minutes above the horizon
BRUCE BRACKENRIDGE
92
and continues to give heat, and it ceases from this
operation for less than half the time.13
[2. The measure
of the atmosphere.]
Thesis 7
But our air, as well as both water and earth (insofar
as it is an element), unless continuously heated, return
at once to their natural condition and grow cold. For
that [teaching] of Aristotle's, that the nature of air
is warm per se, is false.
Thesis 8
For whatever partakes of matter, insofar as it partakes of it, is by nature cold. But whatever is warm
by its own power possesses that nature from an animate force that is either implanted or generated.
[3. The obliquity of the sun's rays.]
Thesis 9
Another and more powerful reason why the sun
warms more when it is high than when it is low is
this: that the low sun strikes our horizon obliquely and
weakly, but the high sun [strikes] more at a right
angle, and more strongly. No one thus far has been
able to explain the reason why the immaterial ray of
the sun behaves here in the same way that dense and
material bodies do when they impinge mutually on
one another.
[4. The numerical evaluation of the three causes.]
Thesis 10
Since, therefore, the sun reaches Prague almost four
times higher in summer than in winter,14 it follows
from this reason and the one mentioned earlier that
on the shortest day there is not more than an eighth
of the heat that descends from the sun to the elements
on the longest day of summer.15
[PROC. AMER. PHIL. SOC.
[5. The heat capacity of the earth.]
Thesis 12
Even though these three causes are indeed most evident on the actual days of the winter and summer
solstices, still on the former the cold will not necessarily be the greatest of all, nor on the latter will the
heat be the greatest of all. There enters in another
cause which by its own right will make winter more
intense from the beginning of February and summer
hotter from the beginning of August, or thereabouts.
For earth and water are dense bodies and cannot be
heated in one moment, and after they have been heated
around the month of June with the sun at its highest,
they retain the heat that has been deeply impressed
upon them (even if they remit some of it nightly from
the surface) because of the density of their matter
and the magnitude of their bodies; and thus they
accumulate the heat of June from the past with that
of July and August. The same thing must be said
conversely about the cold of winter.
Thesis 13
Let the same judgment apply to the second hour of
the day, which is warmer than the twelfth, even
though the sun is already going down. For air exhibits in this instance the same characteristic that
earth exhibited [in Thesis 12]. For air, being very
thin, is changed more quickly than earth, but not
altogether suddenly. At least the surface of the earth,
if not the whole body, shares [in this characteristic].
Thesis 14
From the same principle it can be predicted that
for the same reason September and October will be
indeed warmer than March and February, even if the
length of days will be the same for both.
B. THE MOON: [The physical function of the moon
is to humidify. In addition to monthly moisture cycles,
it also influencesdaily moisture cycles, as witnessed by
the tides.]
Thesis 11
Thesis 15
But not even all of this eighth part of the heat that
remains in winter is of benefit to us. For the sun,
which is elevated only a little above our horizon in
winter, has our dense atmosphere set more in opposition by its obliquity. Let us assume now that the
surface of still air that refracts the solar ray is perpendicularly one German mile from us. (It can
hardly be higher, for is it not that same altitude of
matter that produces the twilight and that refracts the
rays of the stars [ ?]). In summer, therefore, a thickness of one and a ninth German miles is opposed to
the solar ray, and in winter, three and a third [German miles]. Thus the sun's ray in winter is three
times weaker on this account, and with these three
reasons taken together, hardly a twenty-fourth part
of the summer heat remains in winter.'6
Another physical cause of predictions is the moon.
For it has been proved by experience that all things
uniformly moist swell with the waxing moon and
subside with the waning moon. This one fact is the
reason for most of the choices and predictions in
domestic economy, agriculture, medicine, and shipping.
The reason for this natural inclination has not yet been
clearly recognized, according to physicists.
Thesis 16
Now there is a twofold power of the moon: one is
monthly, about which I have already spoken, depending on the changeable appearance of the moon; one is
semimonthly and for that matter even semidiurnal,
which has the greatest force in medical crises and in
the reciprocal tides of the sea, about which [I shall
say] more below.
KEPLER ON ASTROLOGY
VOL. 123, NO. 2, 1979]
Thesis 17
On whatever days, then, the new moon is found
on the calendar, humors insofar as they depend upon
the moon will be diminished; on days of the full moon,
they will be increased. But along with the days
already cited, humors will also be moved strongly at
the quarters. This is a simple and purely astrological
prediction, but if it should be applied to specific fields,
the astrologer would exceed the bounds of his own
profession and would become a farmer, doctor,
chemist, etc.
Thesis 18
But sometimes it behooves those men to be warned.
For instance, I offer this [warning] to chemists: that
the full moon appears unsuitable for the melting of
metals because the air is too humid. Even so, a great
choice of [favorable] aspects will appear for their
work.
C. THE PLANETS: [The physical means by which
the planets influence the earth is the light that comes
down. Insofar as it is reflectedlight it humidifies(as with
the moon), and insofar as it is radiated light it warms
(as with the sun). Further, each type of light can exist
in three degrees: excess, moderation,or deficiency. These
six types differ from the four tactile sense contraries of
Aristotle (hot, cold, wet, and dry) by the inclusion of
the moderate term between the extremes, which is suggested by the example of geometry.]
Thesis 19
The third physical cause of predictions is the varied
nature of the remaining planets, seen in the colors
that they themselves give forth. And we shall be
mistaken here if we distribute the four usual qualities
to the planets. For old and dryness are not positive
dispositions but ones [that arise when] deprived of
light and related life. For cold and dryness are greatest where there is an absence of all light, all life, and
thus all heat. Since, therefore, nothing descends to
us from heaven but the light of the stars, certainly
cold and dryness will not come down by themselves.
[1. The faculties of light.]
Thesis 20
We shall deduce both the diverse forces of the
planets and their number in a manner different from,
though not inconsistent with, Aristotle's [method of
deducing] his four elements from combinations of the
four qualities.'7 Every variation arises from contraries, and the principal variation [arises from] principal contraries. Wishing to philosophize more sublimely and more generally beyond geometry, Aristotle
assumed in his Metaphysics the principal contrary was
that of the Same and the Different. It seems to me
that diversity arises in created things nowhere else
than from matter, or because of matter; and where
93
there is matter, there is geometry. Thus whereas
Aristotle postulated a principal contrary without a
middle between the Same and the Different, I find
that in geometry that is philosophically examined,
there is indeed a principal contrary, but with a
middle; hence what was one term, Different, to
Aristotle, let us divide into two terms, More and Less.
Since, therefore, geometry will have offered a model
for the creation of the whole world, it is quite appropriate that this geometric diversity will work for the
adornment of the world, which depends on the diverse forces of the planets.
Thesis 21
Now, then, since these terms-the Same, the Different, Equal, More, Less-signify nothing per se,
we must think about the subjects themselves. Now
the subjects, or natural qualities with which these
propositions deal, are derived from the following.
Our most discerning Creator made it his priority to
establish a corporeal world. As he first conceived of
creating, therefore, He conceived of matter, which we
know from Moses to have been water, that is, wet,
earthen, and tractable. This, then, is the one natural
quality: namely, moisture. But the body of the world
was not sufficient to the Creator unless something in
some way similar to the Creator was made and
endowed with life and movement. This, then, was
the other quality: namely, life. Now because we are
discussing the forces that the stars exert on bodies
below, we ought to consider whether anything descends to us from the stars. Not matter or body
itself, for that is in our possession before-hand. Not
life itself originally, for all living things draw life from
the movement of the soul which is within them. To
be sure the stars do not generate life, but they help it.
They serve, therefore, the function of an instrument.
They provide us with two instrumental qualities to
correspond with the number of natural faculties: 1)
through the power of humidifying making possible
the tractability of matter, and 2) through the power
of heating making possible the fostering of life and
movement. Both of these powers they possess and
exercise through the benefit of light, which they have
received and send down to us continuously. For the
proper quality of light inasmuch as it is light is heating; but the proper quality of light insofar as it is
reflected, is humidifying.
[2. The variety of possible combinationsof faculties.]
Thesis 22
We therefore have two faculties, heating and
humidifying, with a threefold division, if you will,
excess, mean, and defect. Let us see how much variety
may issue from this. First, there can be solitary
faculties, such as heat in excess, mean, or defect,
BRUCE BRACKENRIDGE
94
and humidity in excess, mean, or defect. Here are
six differences. Then from a combination of both
faculties there arise nine differences, which is clear
from the table given below.
There are, then, fifteen differences in all. Let us
now see which of these are selected and which are
rejected in nature.
[3. The combinations selectively assigned to the
sun, moon, and planets.]
Thesis 23
First it is reasonable that no excess or defect exists
alone without compensation. Of the six solitary
qualities, then, four are eliminated. Indeed the position of mean heat (we shall estimate the mean not
by quantity but by its relationship to the world) has
been assigned to the solar body, which uses purely
its own light; the mean state of humidifying [is
assigned to] the lunar body, which uses purely the
borrowed light of the sun and stars.
Thesis 24
Now, then, excess may not be accumulated readily,
nor may defect. For they are rather estranged from
nature, nor may excesses be received unless they are
tempered with defect. And so no planet has been
made that received either an excess of both or a defect
of both. Seven varieties remain, then, from the combinations. Further, two pairs of these combinations
are reduced to the same thing. For there is the same
proportion between excess of heat and mean of humidity as there is between mean of heat and defect of
humidity; and there is the same proportion between
defect of heat and mean of humidity as there is between mean of heat and excess of humidity, as the
parallel lines in the figure illustrate. There is the
same consideration regarding combined excesses and
defects.
There are, then, five true variations, three simple,
two-as already explained-in a way twofold, but
really with two names, and one with three. And since
there are also five planets in the world, three superior
and two inferior, it is indeed appropriate even on this
account alone (although other reasons may also be at
hand) that they have been made in this number.
Moreover, there could have been nothing more suitable than this distribution of combinations among
them, which distribution I set in plain view in this
chart :18
'
Excess
be
Sun
.
Mean
k Defect
JUPITER
S mer
S S
R
A cu U
rA
TN
M y
VE
JUPITER
S
mer S
R cu U
R
A N r
MVE
y N
JUPITER
Excess
a
Mean
Moon
M
'
Go
Defect
)
[PROC. AMER. PHIL. SOC.
[4. The physical cause for differenceof degrees of faculties for individual planets is attributedto the influence
of the color of the surface of the planet on the reflected
and radiatedlight from the planet.]
Thesis 25
From this chart it follows that the five planets enjoy
not only the borrowed light of the sun, but they add
something of their own as well; and indeed other reasons also support this [assertion]. For if many physical bodies among us have innate light, what prevents
other celestial spheres beyond the sun from having the
same? Moreover, if planets were lacking their own
light, it seems that they would have to change their
appearance, like the moon.19 Finally, it is plausible
that the brightness and twinkling are an argument for
innate light, and cloudiness and inertia, [an argument] for reflected [light].
[4-a Reflected light]
Thesis 26
Now we must consider this point as well: what is
it that can distinguish these forces of planets in
excess, mean, and defect? Since we have deduced
their light as borrowed from reflection, we must consider the varying kinds of reflection on the basis of
the difference that exists on varying surfaces. I am
not speaking now about that reflection that issues from
a mirror and is reflected from any point of it to only
one other point; but rather [I speak] about the reflection that we see from some wall, that is of uneven
and rough surface, which reflects the light with which
it is illuminated, tinged with the color that it [the
wall] possesses, from any point of it onto the whole
hemisphere. For the reflected light of the moon
reaches us in the latter manner, not the former; otherwise we would not see horns on the moon, but always
a small, round image of the sun. Consequently the
geometric
disposition
of the surface causes nothing
except perhaps the dark spots that we see on the
moon.20
Thesis 27
Indeed the causes of one or another reflection (the
cause of quality in the reflected ray) are the colors
of the reflecting surface. Here I would like the
chemists to hear what changes the colors in terrestrial
bodies. The colors of the rainbow are, to be sure,
divided into two classes: one has its source in obfuscation, or deprivation of light; the other, from refraction, or tinting. The source of each class is from the
very light itself or, from a white glow analogous to
light, which, occupying the middle circle of the rainbow, cuts it, as it were, in two.21 From one side it is
diminished, and from the other it is refracted; finally
on both sides it ends in black or darkness. In the
first step of diminution
it becomes yellow,
in the
KEPLER ON ASTROLOGY
VOL. 123, NO. 2, 1979]
second, red, then dusky, and finally, black. The
same thing appears in the clouds either when the sun
has set or is about to rise;22 the same thing appears
in the stars around the horizon; the same thing in
solar eclipses, when our eyes, in which this delusion
occurs, are suddenly deprived of the light of the sun.
In the first step of reflection however, green is seen,
later blue, then purple, and finally utter black or
darkness.23 Since, then, this is the order of colors
in the rainbow, it is appropriate that the same order
follows also in reflection: that a white surface reflects
a ray most strongly, then green and yellow, then blue
and red, then purple and dusky, and surely most
weakly, black.24
Thesis 28
Now black, when it is strongly illuminated, scatters
a red ray. This [phenomenon] appears in mirrors
of steel, when the white color of the face, mixed with
the black of the mirror, presents a rather ruddy
appearance. On this account someone said quite
rightly that the star of Mars was endowed with a black
surface, since its ray is very ruddy. Therefore light
reflected from it is weakened, and therefore it does
not humidify much, and there is a defect of humidity.
By the same argument of color and humidity we
shall assign to Saturn a white and rough surface, because it has a leaden color; to Jupiter a red or
purple surface, because it appears reddish yellow;
to Venus, yellow or white and a very smooth surface, since it is the fairest of all; to Mercury, blue
or green, since it appears silvery, more bright by its
twinkling or diluted brightness than from its color.25
[4-b Radiated Light]
Thesis 29
The intrinsic light itself is varied through the surface of the body whence it has come, so that it gives
now one color, now another, but it acquires the degrees
of heat-producing power from the internal disposition
of its own body. But still even the very surface gives
evidence of the disposition of the body, so that its
power to humidify depends in some way on its power
to produce heat. And clearly if color can be propagated and transferred from one body to another by
the intervention of light, it is credible that other qualities can also be [transferred]; as for heat, indeed,
this [transfer] is most certain. Therefore as each
planet displays power in its effect, it seems appropriate
that there is an analogous disposition in the very body
of the planet. If this holds true, it can lead us to construct wonderful theories. For example, I would say
that in summer it is not healthy to live in the neighborhood of a wall strongly struck by the sun, because
cement is made of lime, and since this [substance]
has the power of corroding and consuming, it imbues
the ray it reflects with this quality. Some trans-
95
parency seems in particular to be associated with
intrinsic light. For if there is intrinsic light in anything, it does not in any case cling to the surface but
has its roots driven into the inmost depths, as we see
in gems. In order for it to shine through, there must
be transparency. To be sure, however, many things
become transparent by heat alone, and these remain
in that disposition.
Thesis 30
Philosophers will forgive me as I draw conclusions
from bodies that we investigate close at hand to
heavenly bodies. For clearly philosophers themselves
disclose no differences at all among those bodies.
Why, as they probably think, should they transfer
base and terrestrial differences with equanimity to
heavenly bodies? But it is preferable to say something that falls into no palpable absurdity than to say
nothing at all. And clearly I am not sure whether
we ought not to call divine and heavenly rather that
quality in the carbuncle gem that produces its little
light, than that elementary quality of the sun's for
heating. Thus I say that Saturn exceeds in humidity,
is deficient in heat, and in the disposition of its body
is like ice (which is itself very humid, since it is
water, and deprived of all heat); hence, its white
surface, and therefore the rather dense and not quite
transparent internal disposition of its body. Astrologers say that it is cold and dry, which comes to
the same thing. But when it works to make summers
rainy and winters snowy it deserves more to be called
humid. We shall assign to Jupiter a body like a
ruby, since it is transparent because of its great
intrinsic light, and even and red because of its brightness and color. Mars will be likened to a glowing
coal from which a latent inner fire shines through;
for astrologers say, and experience bears witness,
that it possesses a torrid and vehement power through
its heat. We shall give amber to Venus with its
uniform and yellow surface because of its exceptional
yellow brightness, since it humidifies so much more
than it heats, which property seems to require a rather
soft body. Finally Mercury will be likened to a sapphire or something similar, because it is suffused with
transparency at the point of its rays and sends out
more intrinsic than borrowed light, because it has the
combination in which heat surpasses humidity.
[5. The applications of planetary properties
to the making of predictions.]
Thesis 31
Thus by reason of borrowed light, or humidity, the
emersions of planets, or their occultations and
oppositions, can be considered. Saturn, being in
opposition to the sun on May 11th and in conjunction with it on November 18th, will exercise its
humidifying faculty most strongly on both dates
96
BRUCE BRACKENRIDGE
because it will turn towards us a face fully illuminated
by the sun. This faculty will be at a minimum on
February 11th and August 9th, when Saturn is in
either quadrature. Jupiter will humidify most strongly
at opposition on April 8th and at conjunction on
October 26th and will be the reverse [weak] at
quadrature on January 8th and July 6th. Likewise for
Mars (although it has very little [power to humidify]), which will be in opposition to the sun on
March 5th and minimal at quadrature on June 9th,
and successively in the intervening and following
periods. The conduct of Venus is different, as is
that of Mercury. For when Venus is at superior
conjunction with the sun on May 15th, it will humidify
most, but before and after, [it will humidify] successively less; and in another year hence it will humidify least at inferior conjunction with the sun. In
this way Mercury will humidify little on January 4th,
April 30th, August 29th, and December 19th. For
at inferior conjunction with the sun it turns upward
its whole face illuminated by the sun. But it humidifies
most on March 9th, June 27th, and October 19th,
when it is at superior conjunction with the sun and
turns its illuminated face downward.
[PROC. AMER. PHIL. SOC.
most motion. The station of Saturn is least efficacious
because it has little motion to lose in its station. Indeed the station of Mercury stirs up winds in general,
and where there are rains and snows it stirs up
copious vapors in kind. We shall expect these
[storms], therefore, around January 17th, April 20th,
May 12th, August 15th, September 6th, and December 9th and 31st. But still the uncertain motion of
Mercury does not allow us to determine the day
beforehand with the greatest certainty.
D. A SUMMARY OF THE PHYSICAL CAUSES
[The role of light as the primary physical cause is
reviewed.]
Thesis 35
Those causes of future events that I have explained
up to this point, even though they do indeed possess
much of the divine, neverthless all resemble the nature
of matter more nearly than those which now will follow. For their method of operating consists in a
certain flowing out of light continued as far as these
sublunary bodies; although this flowing out is without
matter and time, neverthless it is not without quantitative dimensions. For it is made in a straight line;
it is attenuated with distance from a star; it increases
Thesis 32
or decreases with the face of the shining planet; it is
With regard to light and intrinsic heat-giving power, impeded by the interference of an opaque body; and,
there is some doubt whether the high or low planets on the other hand, given the visible presence of the
are stronger. The astrologers prefer high, the star, it flows continuously. This [method of operatphysicists, low. Let us set up a compromise here, so ing] takes place not only in one and the same star,
that the greater the angle at which they are seen but it also applies to a comparison of different stars;
(that is, low), so much more do they heat because of so that since the sun and moon are largest in size,
this very angle of vision. But the power that is in- these powers are most visible on them. In others,
creased by height has another cause.26
whose diameter is small in comparison with that of
the sun and moon, the powers are rather feeble and
Thesis 33
even hardly, if at all, perceptible. The mob of astroloIn regard to the powers of heating and humidifying gers nearly neglects the variations of these effects
we must consider in which sign the planets are turn- according to the methods
specified.
ing. For both the planets and the moon exercise the
SECTION
TWO:
ON GEOMETRICALCAUSES
greatest influence in Cancer because they are longest
above the earth and for other reasons mentioned at [There are three major sources of geometrical causes:
the beginning when I was speaking about the sun.27 aspects, cycles, and planetary harmonics. The animate
refaculty is introducedand is describedas the
Thus, also when they are in the north, they are more ceptor for these geometrical causes, which primary
do not repowerful. Hence full moons are more humid at winter quire the intermediaryof light. The attemptsof astrolosolstices than at summer ones. Thus in northern lati- gers to use the signs of the zodiac to predict events is
tudes for this year and some years to come the already decried; the attemptsof agriculturiststo use astronomical
described powers of Saturn and Jupiter, and even events to predict weather is applauded.]
Thesis 36
Mars at the end of the year, will be weak, because
There follows, then, another cause, which pertains
they will be moving in low signs. But in southern
latitudes they will be so much the stronger.
equally to all planets, nobler by far than that [mentioned] earlier, and one possessing far more wonder.
Thesis 34
For it is not a material cause but rather a formal
Since we observe in motion that whatever is slowest one, and the form which it has is not
simple form,
is most powerful, hence we deduce reasons why sta- but form in animate
faculty, in intellect, in geometric
tionary planets and those in apogee are so powerful. cognition. For [this cause] does not draw its power
The station of Mercury is the most efficacious of all, along straight lines from
single stars, but it takes
for Mercury, being swiftest at other times, loses the into account the
rays of pairs of stars as they meet
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on earth and form a geometric or non-geometric angle.
And this [cause] is not extinguished along with the
very face of the silent moon, when no rays descend
to earth, but the descending ray is then imagined. It
is not impeded when the earth is placed between us
and the stars; but it makes the stars hiding below
[the horizon] also efficacious above. Finally it is
almost instantaneous, and when the angle is commuted
from a geometric to a non-geometric and non-harmonic
one,28it is inactive at once, or a little later, no matter
how much the lights of the stars are increasing.
Since these powers have been confirmed most decidedly by experience, they have supplied me with the
following theories.
Thesis 37
Since God, the Creator of this corporeal world, has
chosen to adorn it with corporeal form, which is
quantity, it is appropriate that the locations themselves, the spaces themselves, and the masses of bodies
have been selected in that mutually proportionate way
that has arisen from the regular kinds of solid figures,
which I have demonstrated in my Cosmic Mystery: 29
i.e., that in truth the motions of bodies, which constitute the life of the world, are all perfectly in tune,
or act strongly in unison, when they take their proportion from the regular planes [of the solid figures].
For as the plane is the representation of a solid, so
the motion is the representation of a body. Just as
in fact in geometry it is impossible that there should
be more than five regular solids, and similarly the
harmonics that arise from a comparison of the regular
plane surfaces cannot be more than eight, as I shall
point out, God willing, at another time in my book
On Harmonics.S
97
aspects [i.e., on the earth] I can attribute to no other
cause than to an animate faculty, which, on the one
hand, is capable of the geometric plan (which shapes
the aspect), and, on the other hand, is in control
of that body on which the influence is directed. For
this [influence] does not come about because rays
join together to form any angle. For pairs of rays
form some kind of angle on the day before and the
day after the aspects, and forever; but the influence
is manifested finally when the angle possesses a harmonic ratio, or schema (Ptolemy says schematism).
But there is no efficient power per se in ratios or
schemata. The same thing obviously happens here
that usually happens in the locomotion of animals.
If one should say that the objects of vision were able
to move the animal as they enter the eye, and that
therefore there was no need of an animate faculty in
the animal itself that was moved, one would be philosophizing strangely.
Thesis 40
Now this faculty, which adds force to aspects, is
not located in the stars themselves. For these aspects
we are discussing touch upon the earth and are a
pure condition flowing not from the formal motion of
the stars, but from the accidental arrangement of pairs
of stars with the earth. In the same way, then, that
the spirit moving the body is located not in the object,
but in the place where the idea of the object is displayed, just so is it necessary for this force, which
makes the aspects powerful, to be located within that
great globe earth, as it is in all the sublunary bodies.
To be sure, every animate faculty is the image of
God the Geometer in creation, and He is inspired to
His task by this celestial geometry of aspects or
A. Aspects [Eight geometricalconfigurationsare listed harmony.
the five traditional aspects plus three new ones.]
Thesis 41
Thesis 38
To thoughtless persons this form of philosophy will
Therefore since there are eight formative ratios of seem new, which it is
not, except insofar as I make
motions, there is some action (or, as it were, motion) a bit more general the ancient philosophic tenets. For,
of heaven on the earth when it meets an intermediating first of
all, as far as the earth is concerned, no one
ray of a star and they then come together on earth to will deny that the form of the whole earth, insofar
form angles; thus the eight harmonic ratios will be as it is an
entity, is nobler than the form that is
expressed in the dimension of these angles. Now recognized in any lump of earth. The works of the
the ancients did not acknowledge more than five [of earth itself show that its form issues from the
species
these angles] (commonly called Aspects): Conjunc- of animate
faculties; these works are the generation
tion, Opposition, Quadrature, Trine, and Sextile. of metals, the conservation of terrestrial heat, and the
But reason soon led me to add three more: quintile,
exuding of vapors for the generating of rivers, rains,
biquintile, and sesquiquadrature,31which many ex- and other meteorological conditions. These [maniperiences have since confirmed.
festations] show that its form is not only preservative,
as in stones, but altogether vegetative.
[1. The Animate Faculty is discussed as the receptor of
the geometric
causes.
It is sensitive to aspects.]
Thesis 39
The reason why the influence of pairs of planets is
so strongly enhanced at the very articulations of their
Thesis 42
Still it is not necessary on this account for the
earth to increase in size or to be moved in location.
For its spirit is not human, nor is it animal, nor plant,
98
BRUCE BRACKENRIDGE
but it is of a peculiar species, which takes its definition
from its function, just as other species of animate
faculties do as well. And the same reason that compelled the ancients to assign a third species of soul
to plants compels us to assign this fourth [species of
soul] to earth.82
[2. The animate faculty is explained by analogy with botanical genetics and naive appreciation of music.]
[PROC. AMER. PHIL. SOC.
is stimulated through the geometric concourse of vegetating rays (which we said warmed and humidified)
so that it applies itself so much more diligently to its
function of vegetation and exudes a copious supply of
vapors.
[3. The characteristics of individual planets influence the
effect of aspects.]
Thesis 44
Thesis 43
But neither is it absurd that animate faculties, which
do not have the advantage of discourse, are appreciative of geometry and are moved by it as if by a certain object. Examples are easily found. The plastic
faculty of a tree does not reason, and yet it carries out
the commands of the Creator to the utmost, in the
arrangement of its leaves for the benefit of the fruit
and for a certain end. Yes, and even all the seeds
retain that beauty which resides in numbers. Most
kinds of plants enjoy five-sidedness; this five-sidedness
is not necessarily transferred principally from the tree
to the apple, in which transformation the preservation
of five-sidedness is impossible; but [it is transferred]
by communication with the plastic faculty, which possesses the inborn beauty of five-sidedness.
But the explanation up to now has been rather
humble and less a cause for wonder, because the faculty
resides within itself, and it propagates the five-sidedness that it possesses. I shall give a more suitable
example. A peasant does not reason what geometric
ratio one voice bears to another voice. And yet that
external harmony of chords flows through the ears of
the rustic into his mind and cheers the man. [And
he is cheered] surely not by a moderation of the
blending of voices, nor by the soft caressing of his
ears (for often the ears ache from a violent sound and
nevertheless they delight in the harmony) nor for
any other reason that could have been discovered up
to now; but [he is cheered] for this reason only, which
I shall demonstrate in my Harmonics: because a
certain geometric ratio produces beauty in the harmonies. [This geometric ratio] belongs to all the
rest of the world and especially to powers that certain ancients called harmonies. Therefore, having
advanced by these examples as if by certain steps,
let us be bold to ascend even to this height: that we
believe that there is in the earth a vegetative animate
power, and in the animate power a certain sense of
geometry that is formal and self-sufficient, because
that power is of the species of animate faculties thatalthough it always inclines towards its own functionis nevertheless more stimulated when this [function]
is refreshed as if with some nourishment of aspects.
In the same way that the ear is stimulated by harmony
to listen carefully and thus to hear much more, (seeking pleasure, which is the goal of feeling), so the earth
Even though the diverse natures of planets explained
above vary the effect of aspects considerably, as at
times the earth is affected by a geometric mingling of
the opposites Saturn and Mars, and at other times
of the similar planets Jupiter and Venus, in almost
the same way that we observe purgatives effecting
a movement of the humors in man's intestines, but
especially rhubarb for the bile. (For is not a faculty
that is capable of geometry also capable of color and
other qualities in its rays?) But the strongest variation nevertheless is from the actual disposition of
bodies, especially the earth, which is different in different places and at different times. For when in
springtime, for example, humors abound in the
northern part of the earth on account of the approach
of the sun, about which we spoke above, then sometimes a very light aspect of any planets whatsoever,
arouses that faculty of the earth to be moved and
to exude some supply of vapors for the generating of
heavy showers. At another time or place the strongest aspect by far may stimulate the earth, but because
of a defect of matter, it elicits very little [response].
B. CYCLES [The secondgeometricalcause is the various cycles that exist both in man for short periods and in
the earth for long periods. The questionof the effect of
eclipses is raised.]
Thesis 45
At this point we ought to understand another additional cause, the ignorance of which strongly disturbs
the predictions of astrologers, since it is not yet
recognized. For just as there are in people certain
periods of humors that cause them to change their
moods repeatedly without any evident cause, so that
sometimes they are merry without music, and again
no pleasure can turn them from their sad thoughts.
Clearly in the same way I perceive that beyond aspects
there are other causes, stronger and more lasting,
which may bring it about that some whole yearand no aspect lasts so long-may be kept in humidity
and hence in extreme cold. [In such a year] you may
see weakest aspects as many times as they fall, exciting
the greatest number of rains and winds; such a year
was 1601. In another year, however, there is such
dryness that on days of aspects nothing can be seen
but little clouds, or mist, in place of vapors; such a
year was 1599.
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Thesis 46
I leave it for consideration whether this very striking diversity comes from eclipses of the sun and
moon (which must also be classified among aspects:
namely, among conjunctions and oppositions). Let
it be established, nevertheless, that the animate faculty
of the earth, about which I have said so much, is
thrown into vehement consternation by the sudden
loss of light and takes up, as it were, a certain mood,
which lasts for a long time; Theophrastus, who is not
always full of fables, also seems to have sensed this
[phenomenon]. For unless you either admit this
[physical] reason, [that there are prolonged effects
of eclipses], or, casting aside all physical reasons
ascribe this ordinary work of nature to the extraordinary providence of God, you will not be able to
explain why eclipses are so ominous.
Thesis 47
It is rather fitting, however, that here the same
thing happens to the earth that happens to living
animals, excepting their mortality, so that from a certain internal disposition, it has cycles of humors, and,
as it were, diseases. If there are such things, laws
and cycles of humors ought to be investigated from
the collected observations of many years, and so
far this observation has not been made. Caesius attributed some significance to the nineteen-year cycle of
the moon, and his opinion is worthy of some credence.
For both the highest tides of the sea are said by
sailors to return after nineteen years around the same
days of the year, and the moon, marked by humors,
seems suitable for this task because it deals with
excess and defect of humors.
C. HARMONIC MOTIONS OF THE PLANETS
[The third geometric cause is the ratio of the motions
(speeds) of pairs of planets. Not much is known of these
harmonies,however.]
Thesis 48
99
D. OTHER CONJECTURED CAUSES [The futile
causes offered by astrologers are contrasted with the
worthwhile causes offered by farmers.]
Thesis 49
Astrologers seek a nonsensical reason for this
general disposition of the years from the entries of
the sun into Aries, for the [disposition of] the four
seasons from the cardinal figures, and for the [disposition of] the months from the figures of lunations;
as though the weather were some abiding object, like
a person, whose birth we can reasonably examine, and
not rather part of the motions of the heavens, or as
though the earth could be restored to a new summer
in one moment. Indeed the earth is changed by
aspects of the vernal figure, if it has any, but only
on that day; on preceding and succeeding days [it
is changed] by other aspects depending upon which
one appears on any particular day. But nothing is
more intolerable in this almost unique concern of certain astrologers than that they distribute with a certain infantile credulity twelve houses among seven
planets beyond every sound and philosophical reason;
they invent tyrannies and momentary vicissitudes of
empires, as if in some assembly of people. From this
[concern] every magical and astrological superstition
has arisen. We shall grant in some places that the
appearance of truth results from this distribution [of
houses], as in Saturn, to which wintry signs are given,
but this [attribute] has other causes; moreover in
other planets, like Jupiter, falsehood is produced. The
astrologer Stoeffler, however, has some time ago
indirectly refuted this trifling side of astrology with
physical reasons (thus no testimony need be sought
from the enemy [of astrology, Pico] della Mirandola);
indeed experience daily refutes it, since after so many
centuries astrologers have hardly ever known the
exact time of equinox, as Tycho Brahe pointed out.83
Let them select some cardinal figures of past years and
let them compare them with [observed] results; I
shall point out to them that they were wrong in the
time, and that even the true figures, examined by this
false method, indicated a contradiction to the [observed] conditions of the following year. In the
coming year the sun enters Aries on March 20th at
sunset as Jupiter rises in Libra; the astrologers will
think that Gemini will be about to rise, according to
the Prussian tables. Nevertheless, no general significance can be deduced from this. For Jupiter indeed
will exert its forces on the 8th of April, when in
opposition to the sun. But on May 10th and 11th
Saturn will succeed it, because it will be opposed to
the sun on that day.
But a third cause presents itself as very likely: the
many sublunary movements of nature which I have
said sometimes occur outside of aspects, are aroused
by the harmonic motion of the planets. For if the
proportionate angle of rays brings this about, why not
also the proportionate motions of pairs of stars, as
often as they are directed towards a harmony, so that
one passes through an equal space more quickly and
another more slowly in harmonic proportion. Now
these ratios are variable, and they do not occur frequently, for the same planet is sometimes swifter and
sometimes slower. Nevertheless this cause has not
Thesis 50
yet been confirmed by experience, nor has a method
yet been constructed by which harmonies of this kind
But here I do not reject the observations of the
may be investigated.
very ancient authors Hesiod, Aratus, Virgil, and
BRUCE BRACKENRIDGE
100
Pliny, and the modern observations of farmers, who
from the annual risings of stars and from the phases
of the moon, make a judgment about future weather
conditions at the time when they observe these phenomena (or not much beforehand). For they observe
these things not as a magic figure in the heavens nor
as a cause of a future disposition (for in other years
they take another prognostic), but as a sign of a general terrestrial disposition now present and continuing
for a little while, but whose periods and laws I contend are not known at another time.
Thesis 51
Still it has been observed that there is a brief cycle
to this succession of universal qualities. For even
peasants (who understand this most shrewdly) expect
a rather harsh winter when they have seen a torrid
summer. And if some period of winter has remained
unnaturally warm, they expect the last part to be so
much the colder. Thus, at a time when winter has
rushed in violently and rather precipitously, spring
will be late in turn, given the agreement of the many
aspects that occur at that time of year.
SECTION THREE: ON PREDICTIONS FOR 1602
[Specific predictionsare made for the weather for each
month in the year 1602. Further there are general commentaries on predictions concerning eclipses, crops, illness, politicaland militarymatters,and earthquakes. The
section concludeswith a discussion of four major aspects
of special significance in the year 1602.]
A. THE WEATHER FOR THE YEAR 1602
Thesis 52
[January]
I have recounted the strongest grounds for astrological predictions; I shall use the remainder as far
as possible, for the predictions themselves. First in
the months of December, January, and February the
sextile of Saturn and Mars will last unusually long,
for it happens that Mars will become stationary at
that time, and Saturn is characteristically slow. There
will be a vehement commotion and a very definite
excess in the atmospheric conditions. But it is not
easy to say how the excess will be manifested. For
in order to know this we would need to speculate on
what the general disposition of the earth will be, which
I think we are not capable of comprehending by any
conjectures up to this time; and this disposition [of
the earth] is stronger than the change in effect of the
planets themselves through their distinctive forces. If
that had been the only aspect [sextile of Saturn and
Mars], I would have predicted extreme cold from the
snowy exhalations. But now because of the coming
together of many aspects, I think that there will be
such a commotion (particularly because Mars is
approaching its station) that the air will clearly be
[PROC. AMER. PHIL. SOC.
warmed by tepid vapors sifted out from the bowels
of the earth, and the snows will be nearly melted, and
journeys will be greatly obstructed. On January
fourth the conjunction of the sun and Mercury will
bring snow or winds according to the general disposition of the earth. Around the tenth or eleventh there
will be six very strong aspects [bringing] pure warmth
and rains mixed with scattered snows. At the end
nothing can be predicted from old aspects, but from the
new ones we predict that the quintile of Jupiter and
Venus will make the twenty-first breezy and warm, as
far as winter allows. On the twenty-fourth the quintile
of Saturn and the sun will bring cold, with snowy or
rainy weather. On the twenty-eighth the sesquiquadrature of Mars and the sun will bring harsh
weather, with biting and harsh winds, and snow for
the time following. Then let those who have a mind
to investigate new aspects observe these days.
Thesis 53
[February]
February springs forth with old and new aspects.
In the beginning the conjunction of Venus and Mercury will introduce disturbances into the atmospheric
conditions. For they also have the contrary nature
of Saturn and Mars, as you have seen above. But
I say this from experience, which testifies emphatically
to their turbulent configuration. Perhaps it may also
be on this account: because their paths are nearly
equal, they are parted slowly and appear somewhat
ponderous. There can certainly be thunderstorms as
well. From the eleventh to the twenty-third of
February there will clearly be no calm. Thus either
it will snow very heavily, if the cold returns on the
eleventh at the quadrature of the sun and Saturn, or
it will rain very heavily, if the warmth lasts that long,
which I rather believe it will.
Thesis 54
[March]
February twenty-first had six planetary aspects
(the moon, being too swift, has hardly any bearing
on aspects). March encounters twenty [aspects].
So the weather will be more turbulent than it was
up to now, since this is also its nature at other times.
The first part of the month will be thunderous and
although the latitude of Mars detracts quite a bit
from its effect, still the frequency of the aspects adds
strength to it in turn. Thus I predict the unusual
warmth up to this point will change to wintry cold
from March thirteenth on; after that there will be
continuous cold winds and snows mixed with rains.
Thesis 55
[April and May]
I expect April to be normal with a warm beginning
on account of the biquintile on Mars and the sun, with
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VOL. 123, NO. 2, 1979]
rain two days preceding and following the full moon,
for all the planets will be in alignment. There will
be rains from the thirteenth to the sixteenth. After
that, heat and around the twenty-fourth such an excess that it will erupt in thunderstorms on account of
the triangle of the sun and Mars. At the end there
will be showers again.
At the beginning of May horrible weather with
thunderstorms will return at the conjunction of Venus
and Mercury unless a different latitude enervates its
power; and this is not certain, nor is the day definite
on account of a faulty calculation up to now. On the
tenth, eleventh, and twelfth there will be cold rains
and on the mountains, either snow or not very healthful air. But if the sky is clear, there is the possibility
of frost to be feared. For beyond the old aspects,
the quintile of Saturn and Mars is approaching from
the new ones. A very beautiful pleasantness follows
with humidity. At the end there will be thunderstorms and showers.
101
moderate, and windy with showers. The eighth day
will be windy and cold, and the ninth and eleventh,
blustery. But the twelfth, thirteenth, and the fourteenth will be troublesome at the conjunction of Venus
and Mercury, which is repeated for the fourth time
in this year, and there will be heavy storms. The
eighteenth, nineteenth, and twenty-first days will be
mixed, with thunderstorms and showers about to
break. From this point, it will be fair and very hot,
for Jupiter and Mars will be in conjunction at the
beginning of August.
Thesis 58
[August]
Finally in August there will be some calm and heat.
On the fifth and ninth days there will be rains [and]
around the fifteenth, cold rains with thunderstorms.
Heat will follow these storms, and on the nineteenth,
there will be a strong disturbance.
Thesis 59
Thesis 56
[September]
[June]
Since the universal cause of the disposition of the
years is not known, I must write about the summer
as if the year, or the earth, will be in the same condition as this year. And since we are in such a state
of ignorance regarding the causes, I think that astrological conjectures regarding any particular period
ought to be forgiven if they are wrong. For we must
not call superfluous those conjectures that are occupied with matters of the greatest usefulness beyond
question, if ever those matters that now lie hidden are
to be brought completely to light. And so I declare
that the beginning of June will be hot and serene;
after the full moon there will be dangerous disturbances, floods, and frequent flashes of lightning. If
the general disposition of the earth inclines towards
dryness, there is no danger. If, on the other hand,
it inclines towards humidity, there will not be flashes
of lightning, but continuous and cold rains. The last
of the middle has been divided as if in continuous stations among their aspects. There will be disturbances.
I should think it likely that the coming month would
be quite cold, because of the great amount of humidity,
if this entire year of 1601 had not been so. If the
year as a whole should be inclined towards dryness,
the degree of dryness will be even greater in this
month.
September will be normal at the beginning. The
eleventh day will be cloudy with rains; the fifteenth
and seventeenth will be humid. But the twentieth
day is rather disturbed by the conjunction of Saturn
and Mars. If a moderate heat has preceded, now
there will be terrible storms. But if the year has been
generally humid, there will be heavy rains with cold
on these days. In general it will be mostly cloudy;
the twenty-seventh day will also stir up the clouds.
The other days will be normal.
Thesis 57
[July]
July has the same appraisal, with the same ambiguity, for it has 18 aspects. Now seeing that there are
around 150 aspects yearly, for the most part these
will be accumulated in the summer half for this
year. The first, second, fifth and sixth days will be
Thesis 60
[October]
There will be cold rains on the fifth of October.
The rest of this month will display the same conditions
as those of the preceding month of September. For,
as it has often been said, it is of great importance to
find out what the disposition of the Earth is for any
particular month. The third, ninth, and twentyseventh days will have storms. The twenty-eighth
and twenty-ninth days will have roaring winds and
rains, but I think that heat will prevail, even though
the nature of certain winds from their own regions
[may be] very cold.
Thesis 61
[November]
In November there will be the usual number of hailstorms, and the fifth will be disturbed with biting
winds. The fifteenth is changeable and warm for
this time of year because of the sextile of Jupiter and
Venus. The eighteenth will have rains, and if it is
clear, there will be the first frost. But I cannot believe
that it will be winter yet. For at the end of the
month Jupiter will be in alignment with Mars and
102
BRUCE BRACKENRIDGE
Venus, making the days still warm and cloudy with
winds, which will cause cold weather occasionally in
some places.
Thesis 62
[December]
I predict that the third of December will be the
beginning of winter, a snowy and cloudy day, but
still not cold. From this time there will be fair
weather, with calming aspects, and throughout this
calm, moderate cold. There will be snow on the
fifteenth. The cold will be unstable on the nineteenth,
and there will be substantial winds and clouds. The
Christmas days will have the sextile of Saturn and
Mars, which will increase the cold; after that, the
sextile of Venus and Mercury will cause snow.
B. ON ECLIPSES
Thesis 63
I have passed over the alignments of the moon with
the planets for the reason stated above. Nevertheless,
I must not omit, also for the reasons stated above, the
meeting of the moon and sun causing an eclipse
[solar eclipse] before the beginning of the coming
year, and also the two ecliptic full moons [lunar
eclipses] on opposite sides of the heavens. [Of the
latter] one will be in 17?48' in Gemini, the beginning
of which, according to an observation carried out here
in Prague, will be on the ninth of December at
5:07 P.M. and end at 8:33 P.M., coming as close as
possible to the calculations of Tycho; the other will
take place on the fourth of June in the year 1602 in
13?32' of Sagittarius, whose beginning will be at
4:52 P.M. on earth. It will begin in complete darkness, and it will end at 9:06 P.M.
Indeed I observed the beginning of the eclipse of
the sun on the twenty-fourth of December at 1: 17,
and the middle at 2: 42 in 2?53' of Capricorn. It was
ten inches from the north. The sun set before the
end. This eclipse is quite notable, and if it is in the
power of eclipses to effect changes, this one will indeed
have remarkable effects, especially in the north,
where it has appeared most conspicuously. But still
I feel that it is uncertain how it will affect the following year. For the instructions of Ptolemy are
dubious, and they do not conform to nature.
In the year 1598 there was quite a large eclipse in
Pisces. When the sun came in the month of September to the opposite constellation of Virgo, there were
copious rains. In the year 1600 there was an eclipse
in Cancer. When the sun returns to Gemini and
Cancer, the weather will be humid both at that season and for the entire summer following. Let the
experts in these matters consider whether the reasoning proceeds correctly: if I neglect the influence of this
eclipse on December of the year 1602 and this winter,
[PROC. AMER. PHIL. SOC.
I shall predict the signs of a great cold. But if eclipses
obtain their force from the configuration of the heavens
(for, granting the influence of the eclipse, one must
also grant the influence of the sign), indeed all three
eclipses occur in aspects of Jupiter and Mars, and on
this account they would signify the adverse effects of
Jupiter: for example, warmth and disturbed humors,
and hence disadvantageous birth.
Thesis 64
Another eclipse of the moon will be seen on the
twenty-eighth day of November in the west, which,
according to the calculations of Tycho, will begin here
in Prague almost with the rising of the sun and the
setting of the moon. And because this [eclipse] falls
within our horizon, as does also the eclipse of the sun
which we in the West will see on the nineteenth of
June, of what use is it to arouse fearful cries about
them? People are certainly ridiculous when they
consider so many eclipses in one year to be ominous; as
if they would not occur four and five times a year if
only we could see the whole globe of the earth. But
men fall into error in this matter, because recently
Origan published his Ephemerides, in which he computed many events occurring over the whole earth;
this is something that others had not undertaken
before him. If it had not been for him there never
would have arisen these fearful voices shouting about
the eclipses within our horizon, for these people,
thunderstruck, look into the sky for something new
when the only thing that is new is Origan's method.
C. ON CROPS
Thesis 65
Predictions about crops are rather uncertain. As
far as natural influences are concerned (we all know
about the providence of God) crops depend partly
upon fortuitous causes, and partly upon that general
disposition of the years discussed above; the former
of which is incapable of being foretold by its very
nature and the latter of which is being investigated in
these pages. The stuff of empty dreams are those
divisions assigned by astrologers to grain, wine, oil,
corn, etc. according to the dispositions of the cardinal
configuration of Jupiter. Do you want to know why
wine has not turned out well this year? Because the
year has been cold and humid. Whoever has made
this observation has understood the effect from this
cause alone. Why was the remaining crop lush in
some places and thin in others? Because, as I have
argued above, some parts of the earth were humid
because of some internal, and up to now hidden, disposition of the earth, and enough of the summer was
fair. But in other places there was dryness, which
was harmful to fruits, and also an earthquake followed.
Sometimes, to be sure, the year is going well, but
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suddenly and in one day either frost or hailstorms do
damage to the mountains, or flooding does damage to
the lowlands when the waters spill over into another
district wherever they are carried by the wind. Hence
it is of the utmost importance to investigate the nature
of winds, whose attacks on these regions of ours are
most inconstant. And so it is very foolish to seek
other causes of these events in the cardinal configurations, when we see them revealed before our
eyes. But lest I seem to be an upstart in overthrowing
this art, I call upon the authority of Cardanus and
Tycho.
Thesis 66
I shall consider one cause, storms, since there is not
yet general agreement about other causes. In southern regions an early spring provokes the trees to
burst into bloom ahead of time, and these still tender
blossoms will be damaged by the advent of an inclement March. In our climate, at that time, nothing
is blossoming because of the usual cold and the north
wind. Spring will bring fruits at the right time, but
the tenth, eleventh, and twelfth of May are in danger,
as stated above. June will threaten the flowering vine,
for both this month and July that follows will see
destruction here and there either from too much
humidity or from hail. August, September, and
October seem favorable for whatever grapes remain on
the vine, and for grain as well. Nevertheless, the
twentieth of September holds danger for that period.
D. ON ILLNESS
Thesis 67
As far as illnesses are concerned, doctors know this
truth universally, that when the air is disturbed, our
bodies are disturbed. Thus, since an inclement winter
is forecast, there will be many people ill, especially in
the beginning of March and May. But if the summer
appears turbulent, the following autumn will be quite
bad, because of the conjunction of Saturn and Mars,
and there will be many autumnal illnesses, and plague
in some places brought in by the wind, especially if
one considers the eclipses, about which I have spoken.
I have noted some days that are troubled in general by
close aspects; these will incite illnesses in likely subjects, and those already ill will become worse.
But if someone collapses now, or if harmful humors
are flowing in the body at this time, then clearly one
should not neglect, as I have done up to now, the
configurations of the moon with the planets [and]
especially with the sun. For in a very particular way
they order and move the humors, (to which that
great chaos of humors, the ocean, testifies), and I
would affirm that configurations ought to be considered in the advantageous practicing of medicine.
Doctors, if they can, will leave an invalid alone who
103
is terribly weakened, when the moon is turning in
a strong aspect. For any aspect whatever is a purgation of nature in its own right. But if strong purgations are needed, one must select strong configurations. Furthermore, the whole matter of crises clearly
depends upon the revolution of the moon and upon
its configuration with the planets, and it will be sought
elsewhere in vain.
E. ON POLITICALAND MILITARY MATTERS
Thesis 68
Astrology clearly has some say in political and military matters, given those statements I have set forth
above in the passage on fundamentals regarding the
agreement of human dispositions with celestial configurations. For every kind of human disposition that
has been roused to lively activity naturally by its own
motivation will be moved to vigorous activities in
strong aspects, especially if the aspect has a similarity
of origin with the particular individual under consideration. This "sympathy" arises not from the
temperament of the body, as though the sky should
set it into motion through the air, and this should act
on the temperament of the body, and this should act
on the mind; but, on the contrary, the mind of its
own accord shares feeling with the sky, because it
[the mind] possesses cognition with light and harmony; yet later it alters the body as well. Furthermore, since a person is a social animal, dispositions
are particularly oriented to a public undertaking when
those rays of planets are oriented geometrically in the
heavens. But this task may be undertaken more
accurately if there are ready at hand the horoscopes
of those who (if I may use a Tychonian phrase)
govern public destiny.
Thesis 69
It is very foolish, however, to look here for those
particular matters, the number and quality of which
the curious seek in the almanacs. For what I have
said about meteorology should hold here as well:
nothing can be sought from astrology than a certain
driving force of dispositions; whatever will happen
in human affairs is in the power of people's free will,
which is the image of God and not the offspring of
nature and in the power of other causes. Therefore,
as to whether there will be peace or war in any
particular region, let those judge who are skilled in
political affairs, for they have no less skill for predicting than does astrology. Certainly political affairs
have their own character as much as the flowing
motion of the heavens.
But if there is war in any region, the dispositions
of soldiers and leaders will be disposed towards stratagems, battles, attacks, and other movements especially on the following days: the twelfth of January;
BRUCE BRACKENRIDGE
104
the fifth, fourteenth, and twenty-fourth of February;
the fifth and fourteenth of March, the fifth and twentyfifth of April; and fourth, twelfth and thirty-first of
May; the ninth and twenty-first of August; the
twentieth and twenty-seventh of September; the third
of October; the fifth, eighteenth, and thirtieth of
November; and the twenty-fifth of December. And
experience confirms this view.
F. ON EARTHQUAKES
Thesis 70
Earthquakes, whether rather notable or completely
unheard of, do not seem to be indicated by the heavens
since Saturn and Jupiter will not be in alignment this
year; however, the sky is only one very general cause
and sign of great earthquakes.
For more often specific and natural events occur in
sublunary affairs which it is not the province of astrology to predict. Consider, for example, the earthquake
that occurred in September of last year, 1601, which
shook most remarkably the entire district of the Rhine
and regions nearby. They say that its force was felt
even in Lombardy. These [occurrences] I predict,
not from astrology, since an earthquake is not of the
stars, but from observation of the earth and all the
seasons, from which it is clear that the movements of
troops and human dispositions are [also] wont to
follow.
G. ON FOUR MAJOR ASPECTS OF SPECIAL
SIGNIFICANCE IN 1602
Thesis 71
Four astrological events of particular importance
may be added here: the eclipse of the sun in 3? Capricorn; the sextile of Saturn and the stationary Mars,
which lasts throughout almost all of January and
February and returns in the month of June; the conjunction of Jupiter and Mars at the end of July;
and the conjunction of Saturn and Mars in the month
of September. First, experience shows that under
these two conjunctions souls are generally stunned
and frightened, or aroused in the expectation of
revolts, and this fact is very significant for a multitude
of people congregated in one place either for some
undertaking, or for destruction, as military experience
testifies. The defeat at Eger34 in the year [15]96
occurred at the opposition of Jupiter and Mars; likewise, [the massacre] at the marriage in Paris35 in
the year 1572 occurred at the conjunction of Saturn
and Mars. I would think that it is not entirely useless
for leaders and rulers of people to be taken up with
such considerations; for in order to rule the multitude
one must have great skill and an awareness of those
forces that affect human dispositions in a group. Thus
if it is preferable for peace and quiet to prevail, and
[PROC. AMER. PHIL. SOC.
sedition is feared, let meetings not be held in August
and September, or let them be broken up, or better
yet, let the causes exasperating people's dispositions
be taken quickly away, or by the introduction of some
new deterrent, let their minds be changed. If some
bold venture must be undertaken and must be accomplished by exciting terror, let August be chosen.
If the mind must be hardened for some labor, let
it be in September.
But if in these months the enemy should dare some
boldness, take up suitable remedies to guard against
consternation in the minds of the people. For these
remedies are always in our power, however things may
happen, and nothing is absolutely predestined. Certainly the past year has testified to this with a very
clear example.
Thesis 72
Then, a great safeguard for the army lies in their
loyalty to and high regard for their commander; for
every victory depends on a driving force of the spirit.
If, on the other hand, the leaders should be held in
contempt because of an agitation of their horoscopes,
danger through their own fantasies would afflict the
army and the fortune of war. Thus when the conjunction of Saturn and Mars falls in Poland at sunrise,
and the eclipse of the sun is strongest in Moscow and
Poland, and if there is already war there, I think
that defeat is predicted by that aspect. If someone
should accommodate this agitation of the horoscope to
his own strengths, he himself may inflict defeat; but
if a strong peace grows firm in the meantime, clearly
there is no danger from the heavens alone.
Thesis 73
In the third place, the conjunction already mentioned affects our country as well; since it is very
spacious, not only the sky, but sublunary causes affect
certain sections. For although the sun shines upon
and warms the whole world, yet it does not produce
olive trees everywhere, except where they have been
planted. But yet because of an earthquake and horoscopes, and eclipses of the sun, which affect the sun's
position for France and Spain, we shall await some
event touching Sweden, Switzerland, Lombardy, and
nearby France in particular.
Thesis 74
I have therefore added the sextile, as well as the
conjunction of Jupiter and Mars because they affect
certain political horoscopes. Thus they will be active
in this year; whether happily or unluckily (as God
wills) they themselves may judge.
Still, the fiery planet Mars can afflict a person's natural disposition, if he or she is not exceedingly strong,
when it wanders around Virgo for a long time, and
when in opposition to the sun in March it disturbs the
natal day.
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VOL. 123, NO. 2, 1979]
Thesis 75
I know that astrologers are accustomed to predict
the death of some outstanding military leader from
the conjunction of Jupiter and Mars, which falls on
the seventeenth of Libra, especially if he should have
some particular disposition of his horoscope there.
Lest this practice be judged as slander, as if heaven
might be said to be founded for afflicting mankind,
it [the prediction] must be explained otherwise. For
this is the true meaning: that since this aspect is
fiery per se and is one of the bright planets, thus
experience testifies that it is found in illustrious
families.
But when almost every agitation of body or mind
occurs, or a transition is made to a new status when
heaven corresponds to the horoscope (which is especially evident in births), it often happens that some
illustrious people are moved under these and similar
aspects, since the number of people born under such
aspects is so great. Indeed the very same agitation,
just as it gives those badly disposed over to destruction, just so it moves the stronger ones, either by
reason of age or health, to great accomplishments.
And each of these groups can also become affected in
opposite ways in this year, but nothing is clearly
inevitable.
CONCLUSION
I have dealt in this book with what I felt could
be discussed and defended about the fundamentals
of astrology and about the coming year 1602 on the
basis of physics. Now if the professors of physics
think that these fundamentals are worthy of consideration, let them communicate their criticism to me, so
that we may discover the truth; and I shall answer
them, God granting me the faculty, with prognostics
for the following year. Furthermore, I urge all those
philosophizing seriously to participate in the effort.
For it involves the honor of God the Creator and the
advantage of the human race. Meanwhile I heartily
wish one and all a Happy New Year through Christ
our Mediator.
GLOSSARYOF PROPER NAMES OF
PERSONS AND PLACES
Aratus
(ca. 315-240/239
B.c.):
He composed
an
astronomical poem entitled Phaenomena, of which
one section deals with weather signs (Prognostica).
This work was widely read by both Greeks and
Romans until the end of antiquity. Hipparchus (ca.
190-120
B.C.), the great Greek astronomer who was
held in such high esteem by Ptolemy, wrote a commentary on this poem. It is, in fact, the only existing
work of Hipparchus, who is otherwise known to us
largely through the writings of Ptolemy.
Aristotle
(384-322
B.C.):
The works of Aristotle
provide the major link between Greek science and
105
philosophy and the scholarship of Europe during the
second millennium. They form the basis of the
scholastic tradition in which Kepler was trained and
the tradition in which he argued for change (see
Notes 17 and 32). English translations of his entire
works can be found in the Loeb Classical Library
(Rackham, 1945) or in The Works of Aristotle Translated Into English, edited by W. D. Ross, which also
appear in Volumes 8 and 9 of The Great Books of the
Western World.
Brahe, Tycho (1546-1601): Kepler joined Tycho
in Prague at the beginning of 1600. He was the
major source of the astronomical data used by Kepler
(in particular, the data on Mars was the key to
Kepler's New Astronomy). Tycho had constructed
observing equipment of heroic proportions, and his
data, good to about two minutes of arc, was almost an
order of magnitude better than that of Ptolemy. The
best biography is by J. L. E. Dreyer (1963), who also
edited the collected works of Tycho (Dreyer, 1913).
Partial English translations can also be found in
Boas, 1959 and Shapley, 1929, pp. 18-19. See the
entry in this Glossary under Rosenberg for a description of Tycho's death.
Bulder, D. Herman (contemporary of Kepler's): As
described by Kepler, he appears to have been an
astrological consultant of sorts to Baron von Rosenberg, to whom this work is dedicated.
Caesius
Bassus
(First
Century A.D.):
He is men-
tioned in the life of the Roman satirist Persius (Satire
6) as one of his intimate friends; he is classed with
Horace as a lyric poet by the Roman educator Quintilian in his Institutio Oratoria (10.1.96); Caesius was
killed, according to the Scholia, in the famous eruption
of Vesuvius. (Conington, 1893).
Cardanus (Cardan, Jerome) (1501-1576): Although
he wrote more than 200 works on medicine, mathematics, physics, philosophy, religion, and music, his
fame today rests on his contributions to mathematics. In 1570, Cardan was imprisoned by the
Inquisition. He was accused of heresy, particularly for
having cast the horoscope of Christ and having attributed the events of His life to the influence of the stars.
After a few months in prison, having been forced to
recant and to abandon teaching, Cardan went in
1571 to Rome where he obtained a lifetime annuity
from Pope Pius V. During the last year of his life
he wrote an autobiography that, in the words of one
observer, "did not shrink from the most shameful
revelations." For Cardan's work in magic, alchemy,
and the arts of divination, see Thorndike, 1923: v, pp.
563-579.
Cicero: (106-43 B.C.) : Prolific writer, lawyer, statesman, and philosopher, he was the first important prose
106
BRUCE BRACKENRIDGE
[PROC. AMER. PHIL. SOC.
author to introduce Greek philosophy to Roman readers, and he created a Latin philosophical vocabulary.
Translated Aratus's astronomical poem, Phaenomena.
His philosophical work On the Nature of the Gods
contains information on the scientific knowledge of his
time. In two other books, On Divination and On Fate,
superstition is differentiated from religion, and determinism from fatalism. Cicero states that he was led
to write his philosophical works through his determination "to help his fellow citizens" and "never to stop
seeking the good of the community." These works
have had their main influence as practical guides to
the good life. (Dorey, 1965).
Natural History, a complete encyclopedia of the science
of his period. Included along with geography, botany,
biology, metallography, etc., were descriptions of the
practice and utility of various forms of magic. The
lion, the unicorn, and the phoenix were all described
and accepted at apparently the same level of credulity.
Pliny also notes, "It is generally admitted that all
water is more wholesome when it is boiled," and his
English translator of 1856 commented, "This is not
at all the opinion of the present day." Perhaps the
various cholera epidemics of the nineteenth century
might have been prevented if we had not thrown out
his boiled water with the unicorn.
Hesiod (Eighth Century B.C.): A didactic poet
thought by the Greeks to be one -of the earliest teachers and civilizers of man, Hesiod composed two major
poems. The first, Works and Days, is filled with
moral precepts and contains a description of a year's
farm work (farmer's almanac). Proper times for
various operations are indicated by the positions of
constellations, migrations of animals, etc. He also
gives advice on navigation and names certain days
lucky or unlucky for various operations. The other
poem is the Theogony, the first work of conscious
religious writing in Greek. These works and The
Shield of Herakles (of disputed authorship) are available in translation. (Lattimore, 1959).
Kepler (1571-1630): It is generally conceded that
the best biography of Kepler is that by Max Casper,
first published in German in 1948. It is now available
in an English translation by C. Doris Hellman
(Casper, 1959). The English edition by Dr. Hellman also contains an excellent bibliography of
Keplerian studies and translations. An excellent
shorter biography and a selected bibliography by Owen
Gingerich appear in the Scribner Dictionary of Scientific Biography. An interesting popular biography of
Kepler is The Watershed by Arthur Koestler (Koestler, 1961), which has been taken from the larger work,
The Sleepwalkers, by the same author (Koestler,
1959). Both are now available in paperback editions.
Prague, Bohemia: A city in what is now Czechoslovakia. Kepler moved here at the beginning of 1600 to
join Tycho Brahe. It was here that On the More Certain Fundamentals of Astrology was written, as well as
his great work on astronomy, The New Astronomy.
Origanus, David (1558-1629): A teacher of Greek
and mathematics at the Academy in Frankfort-on-theOder, Origanus compiled ephemerides for the period
1595 to 1655 that contained in the preface a listing
of all the eclipses that were to occur in each year.
Pico della Mirandola (1463-1494): An Italian humanist who argued against astrology on religious,
philosophical, and scientific grounds (it denied the
omnipotence of God, it denied free will, and it was
strikingly inaccurate). He pointed out that the
astronomical basis of astrology would be shattered
when astronomers adopted the Copernican system, as
he believed they would. (See Note 18).
Pliny (A.D. 23-79): The elder Pliny was a Roman
statesman who produced among other works, the
Ptolemy, Claudius (A.D. 100-170): The life of
Claudius Ptolemy is almost unknown despite his fame
as an astronomer and geographer. His works in
astronomy (The Almagest) and in astrology (The
Tetrabiblos) were used and preserved by the Arabs
during the so called "dark ages" and served, along
with Galen's work in medicine and Aristotle's work
in biology and physics, as a major link between Greek
science and European science of the second millennium.
The only English translation of the Almagest appears
in Volume 16 of The Great Books of the Western
World (Ptolemy, 1952), and a translation of the
Tetrabiblos is in the Loeb Classical Library (Ptolemy,
1940).
Reinhold, Erasmus (1511-1553): After Copernicus,
Reinhold was the leading mathematical astronomer of
the sixteenth century, and in computational ability
he surpassed Copernicus himself. In 1551 he produced the Prutenic Tables, which contained astronomical data based on calculations from the Copernican model. (Gingerich, 1973: pp. 43-62).
Rosenberg, Petrus Wok de (ca. 1600): "Peter Wok
von Rosenberg was the leader of the Utraquists. As
the last of one of the most powerful and richest families of Bohemia, he led a lavish life in splendor and
luxury and squandered colossal sums on his alchemical
passion. After Brahe's death, Rosenberg transferred
his friendship for him to his successor. Kepler gave
evidence of his gratitude by dedicating to him the first
work he published after his change of residence to
Prague. It was an essay about the more reliable
foundations of astrology." [M. Casper, 1959: p. 161].
It was, in fact, at Baron Rosenberg's table that the
great Tycho set the stage for his dramatic demise.
Kepler reports in his Diary of Observations:
On 13 October,Tycho Brahe, in the companyof Master
Minhowitz,had dinnerat the illustriousRosenberg'stable,
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VOL. 123, NO. 2, 1979]
and held back his water beyond the demands of courtesy.
When he drank more, he felt the tension in his bladder
increase, but he put politeness before his health. When
he got home, he was scarcely able to urinate.
At the beginning of his illness, the moon was in opposition to Saturn . .. [follows the horoscope of the day].
After five sleepless nights, he could still only pass his
water with the greatest pain, and even so the passage was
impeded. The insomnia continued, with internal fever
gradually leading to delirium; and the food he ate, and
from which he could not be kept, exacerbating the evil.
On 24 October, his delirium ceased for several hours,
nature conquered and he expired peacefully among the
consolations, prayers and tears of his people. [Koestler,
1959: p. 315].
Stoeffler, Johannes (1425-1531): A professor of
mathematics, astronomy, and geography at Tubingen.
He published an account of an astrolabe of his own
construction and other scientific works.
Theophrastus
(372/369-288/285
B.C.):
Peripatetic
philosopher, scholar, teacher, and writer, he was
Aristotle's successor as Head of the Lyceum. He continued Aristotle's encyclopedic purpose, and his activ-
ities were prodigious. In addition to his great work
on the history of physics, he wrote scientific treatises
on meteorological subjects, such as "On Weather
Signs." The Characters is a popular collection of
thirty brief character sketches describing human foibles
in exaggerated descriptions (the avaricious person,
the loquacious person, etc.). Kepler probably alludes
to this work in his term "full of fables" (Thesis 46).
A translation of the Characters is found in the Loeb
Classical Library (Edmonds, 1929).
Virgil (70-19 B.C.) : A great Roman poet and leading
naturalist of his time. In addition to his epic, the
Aeneid, and the pastoral poetry of the Eclogues,
Virgil also wrote an outstanding scientific treatise,
the Georgics. It is divided into four books: 1, agriculture in general; 2, trees, especially vines and olives;
3, stock farming; and 4, bee-keeping. These works,
as well as minor poems, are translated in two volumes
of the Loeb Classical Library (Fairclough, 1930).
NOTES
FOREWORD
AND PREFACE
Note 1. Neugebauer, 1969: p. 171.
Note 2. Ptolemy, 1940: p. 3.
Note 3. LaPlace, 1829: p. iii.
Note 4. Duhem, 1969: p. 5.
Note 5. Neugebauer, 1969: p. 204.
Note 6. Kepler, 1952: p. 850.
Note 7. Kepler, 1952: p. 926.
Note 8. Simon, 1975: p. 446.
Note 9. Kepler, 1858.
Note 10. Kepler, 1938 4: pp. 8-35.
Note 11. Casper, 1959: pp. 391-396.
Note 12. Gingerich, 1973: pp. 289-312.
107
NOTES ON TRANSLATION
SECTION ONE
Note 13 (Thesis 6)
The time of elevation of the winter sun, 7 hours
and 49 minutes, is correct (as is demonstrated below).
Thus the length of time the winter sun is set is 24
hours minus this time or 16 hours and 11 minutes,
which is just about twice the time of elevation. Since
in summer the situation is reversed, it would therefore appear that the time of elevation of the summer
sun is 16 hours and 11 minutes not 22 minutes as
given here.
The first drawing is a hemispherical cross section
that locates Prague at noon on the summer solstice,
The earth's axis is inclined at an angle of 23.5? with
respect to the plane of the earth and the sun; Prague
has a latitude of 50.096? (50? 5' 45"). The line
CC' is the projection on the cross section of the great
circle on the earth that represents the border between
light and dark. The point p is the intersection of the
line AB and the line CC'.
Earth s
location
\s
of Prague at noon on
the winter solstice)
0-
b.-
Border between
light and dark
The second drawing is a cross section of the earth,
sliced from point A to B (Prague) in the preceding
drawing. The arc ab taken in a clockwise sense represents the angle for which Prague is dark in the
summer. (Recall the meaning of the point p from
the previous drawing.)
a
B
a
-0
U-
q
96
108
BRUCE BRACKENRIDGE
Thus one has from the second drawing
[PROC. AMER. PHIL. SOC.
Thus the relative height of the summer and winter sun
in the proportion of the angles of incidence at noon, or
cos OD = qP/qA
and from the first drawing
Ratio
qA/r = sin 39.904? = 0.64150
or
qA = 0.64150r.
Further
qO/r = cos 39.904? = 0.76712
or
qO = 0.76712r.
Finally
qP/qO = tan 23.525? = 0.43532
63.40
16.4 = 3.87 or approximately four times.
Note 15 (Thesis 10)
The combined effect is the product of the two ratios;
thus the winter heat is diminished by i due to the
decreased time of elevation and by - due to the
obliquity of the sun's rays or a product of -.
Note 16 (Thesis 11)
For this calculation we assume the German mile
to be the order of 3 or 4 English miles. Thus the
radius of the earth is roughly 1000 German miles.
The following figure again shows the summer and
winter drawing of the earth's atmosphere.
or
qP = 0.33394r.
Thus the cosine of ODis given by
cos OD= qP/qB
= 0.33394r/0.64150r
= 0.53057
or
20D = 117.258?
The time TD the summer sun is set is given by
117.2580
X 24 hours = 7 hours 49 minutes
3600
TD = 117.2
and the time TL summer sun is risen is
TL = 24 hours - TD = 16 hours 11 minutes
The effective thickness of the atmosphere at noon
on the summer solstice is the distance AB'. From the
law of sines one has
Note 14 (Thesis 10)
The following drawing is the same as the first
cross section in Note 1. At point A it gives the angle
between the horizon and the sun's rays at noon in
Prague for the winter solstice (16.4?) and at point B
for the summer solstice (63.4?).
The ea]th's axis
on
sin 153.429?
sin Z OB'B
OB'
OB
where
OB' = 1001 German miles and
OB = 1000 German miles.
Thus
1000
sin Z OB'B = 1001 (sin 153.429?) = 0.44686
1001
thus the angle is given by
ZOB'B = arc sin 0.44686 = 26.542?
The angle BOB' is given by
Z BOB' = 180 - 153.429? - 26.542? = 0.029?
Again from the law of sines
sin 0.029?
BB'
sin 153.429?
1001
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VOL. 123, NO. 2, 1979]
OR
BB' =
/ sin 0.029? \
/0.0005061\
= 1001
0.4473
1001sin 153.429?)
= 1.1 German miles
Which is the one and one ninth (1.1) given by Kepler.
Repeating the calculation the winter thickness AA'
sin Z OA'A
1000
sin 106.379
1001
OR
1000
/ OA'A = arc sin 1001 (0.95942) = 73.427?
Thus the angle AOA' is given by
Z AOA' = 180? - 106.379? - 73.427? = 0.194
sin 0.194?
AA'
sin 106.379
1001
OR
AA' = 1001
0.003386
= 3.5 German miles
0.9594
which is a bit more than three and a third (3.3)
German miles for the winter thickness given by
Kepler. In any event, if one assumes that the ratio
of the effective thickness is about 1, and then multiplies by the factor of -1 from the three other causes
discussed in Thesis 10 (see Note 15), one has a
"twenty-fourth part of the summer heat that remains
in winter."
Note 17 (Thesis 20)
Aristotle's discussion of the four elements (air,
earth, fire, and water) appears in the third of the
four works that comprise the body of his "physical
science." (Physics, On the Heavens, On Coming into
Being and Passing Away, and Meteorology). In the
first work contraries are established as principles in
natural philosophy and, in the general sense of Excess
or Deficiency (similar to the Same and Different employed by Plato in the Timaueus),are refined by Aristotle into the principal contraries of Form and Privation.
In the third work, the tactile sense is identified as
by far the most important of the senses, and four
qualities, the "tactile sense contraries" of hot, cold,
wet, and dry, are introduced to derive and explain the
behavior of the four elements. These four elements,
and in fact these four qualities, had long been employed by Greek natural philosophers. What is new
is that Aristole assigns two qualities to each element
(earth is cold and dry, water cold and moist, air moist
109
and warm, and fire dry and warm), and he permits
one element to transform into another by replacing
one quality with its contrary.
In the section to follow, Kepler must supply a
physical model to account for the astrological powers
of the planets. To do so (see Note 18) he requires
three degrees of heat and three degrees of warmth;
the Aristotelian system of two degrees of each does
not supply him with enough options to describe all
five planets. Thus he appeals to geometry for the
existence of a mean between the two extremes to provide the needed versatility.
Note 18 (Thesis 24)
The astrological powers of the various planets (i.e.,
Mars is hot and dry, while Venus is warm and moist)
have been well established by their "successful" usage
over the ages. What is in question here is not the
validity of the choice of particular powers but rather
how they are to be reasonably derived. Ptolemy
accounts for them by the planet's proximity to the
two luminaries, the sun and the moon, and to the
moist exhalations about the earth. [Ptolemy, 1940:
p. 35] Ptolemy, however, places the earth at the
center of the system and arranges the luminaries and
the planets in order of their periods of motion about
the earth (the longest period is assumed to represent
the most distant planet); arranged in this way, the
sequence is: the moon, Mercury, Venus, the sun,
Mars, Jupiter, and Saturn. Thus Mars and Venus
are similar in warmth by virtue of their proximity to
the sun; they differ in moisture, however, since Mars
is removed from the moon while Venus is relatively
close to it.
Kepler, however, has adopted the Copernican system in which the sun and earth exchange places
(sun, Mercury, Venus, earth and moon, Mars, Jupiter,
Saturn). Thus, Mars is not only removed from the
sun, but is in fact very close to the moon. Nevertheless, Mars must still be hot and dry because astrological experience has shown that it is hot and dry.
Kepler is to offer physical reasons to supplant
Ptolemy's luminary proximity based upon the optical
properties of the surfaces of each planet (these are
discussed in the Theses 25-30). The chart that is
given here in Thesis 24 simply displays the astrological
powers of the planets and attests to their uniqueness.
Critical to this ordering is the inclusion of a mean
state between the two Aristotelian states of excess
and defect (see Note 17). This chart, however,
appears in part to be at odds with the text. Since
the chart was set by the printer and since it contains
a complicated and convoluted set of interworked
words, perhaps it is not unreasonable to assume that
it may contain typographical errors.
The following is the chart as it appears in the
BRUCE BRACKENRIDGE
110
there appears to be some contradiction within the
text itself as well as between the chart and the text.
The chart for Mars and Saturn, however, is clearly
in error. They are shown as follows:
original Latin text:
I V P I T E R
Excessus
cu
A
T N
VE
u
Sol.
V
V
ri
4-
0)
S
mer
u
Rcu
A
N
R
M
us
R
Excess
m
Mediocritas
E
)
0,
Luna.
CL
S
h*
V N
ri
Sun
e I Mean
Moon
V
cu S
M VE
I V P I T E R
Defectus
-
A
I V P I T E R
Mediocr.
Excessus
S S
S mer
[PROC. AMER. PHIL. SOC.
Defectus
From this chart a simplified version of the chart
for Mercury and Venus can be constructed:
EE
r:
Moon
.
60
oq
SuK
These are the combinations of warmth and humidity
that are referred to in Thesis 24 as "two-as already
explained-in a way twofold, but really with two
names." They have been previously described in this
thesis as follows: "Two pairs of these combinations
are reduced to the same thing. For there is the same
proportion between excess of heat and mean of humidity as there is between mean of heat and defect of
humidity."
The chart for Jupiter can be redrawn as follows:
Defect
L.
Thus Mars would be cold and moist and Saturn
hot and dry; clearly this drawing is at odds with all
that has gone before and all that is to follow since
"Saturn exceeds in humidity (and) is deficient in
heat." [Thesis 30] Note, however, that Saturn's
function is described by Ptolemy as "chiefly to cool
and moderately, to dry, probably because he is furthest removed from both the sun's heat and the moist
exhalations of the earth." [Ptolemy, 1940: p. 35]
In this description of Saturn's dryness, Kepler is
moderately at odds with Ptolemy.
Also there is confusion concerning the number of
true variations. We are told in Thesis 24 that "there
are, then, five true variations, three simple, two . . .
in a twofold way, . . . and one with three." Since
the twofold and threefold have to be identified with
Venus, Mercury, and Jupiter, the simple variations
appear to be those associated with Mars and Saturn
(simple in the sense that there can only be one transition for each). Further, if there are only two simple
variations instead of three, one has the proper sum
of five possible variations.
It would appear then that the correct drawing for
Mars, Saturn, and Jupiter should be as follows:
r
Excess
Jupiter
Excess
Sun
U
N
Mean
<
Jupiter
Excess
Excess
Mean
Moon
>
Sun
E Mean
piter
Jupiter
Mn
oo
rt
Defect
Jupiter
Defect
DefeDefect
K
Def
/
It would appear from the text, however, that there
should be only one line for Jupiter: that line from
mean heat to mean humidity. We are told in the
opening of Thesis 24 that "Excess may not be accumulated readily, nor may defect. . . . And so no planet
has been made that received either an excess of both
or a defect of both." In the next paragraph of this
thesis, however, we are told that one of the five true
variations has one name but with a threefold variation, presumably Jupiter with the three levels. Thus
Note 19 (Thesis 25)
Here Kepler is arguing that if planets only reflect
light, then they should show phases, such as the moon.
He is soon to change his opinion, however. By 1609
Galileo employs his telescope to view the planets, and
soon the phases of Venus are established. In his
Letters on Sunspots, Galileo states, "The opaqueness
of Venus is indubitably proved by the single experience
I reported in my first letter (The Starry Messenger,
1610): namely, our seeing Venus vary in shape as
VOL. 123, NO. 2, 1979]
KEPLER ON ASTROLOGY
does the moon." [Drake, 1957: p. 153] Kepler recognizes and accepts this new evidence in his Dissertation
on the Starry Messenger. The planets, like the moon,
are opaque; only the sun and the fixed stars emit their
own light. There is, however, some indication that
Kepler had earlier begun to change his mind on this
issue. In 1607 he had considered in a letter the
assumption that the planets might be opaque like the
earth and, in fact, might even be inhabited. In this
work of 1601, however, he clearly adopts the position
that planets both radiate and reflect light.
Note 20 (Thesis 26)
The Aristotelian position requires that the moon
and all objects beyond the lunar sphere be perfectly
spherical. Kepler argues here that if the surface of
the moon were of a hard, smooth, mirror-like quality
we would not see the entire surface illuminated but
rather we would see the image of the sun only as a
bright point. Later, Galileo also makes use of this
argument. [Galileo, 1970: p. 70]
Note 21 (Thesis 27)
In what is to follow, Kepler develops an early version of a subject that is to be of interest to him
throughout his life: the explanation of the colors of
the rainbow. Here he divides the rainbow into two
equal sections and offers a different physical cause for
each half. The common source is light itself, or to
be more precise "a white glow analogous to light"
which occupies the middle of the rainbow. Since the
center of a single rainbow is in fact not white, the
"source" itself is not visible, but only its effects.
Note 22 (Thesis 27)
The colors on this side of the rainbow are attributed
to obfuscation, or in contemporary terminology, "scattering." The current explanation for this effect has
light scattered by particles in our atmosphere, the
short wave lengths (blue) are scattered more than
the long wave lengths (red). Hence "the sky is blue."
As the sun sets, its rays must pass through more and
more of the atmosphere, and hence more and more
blue is scattered from the white light leaving it to
appear first yellow and then red. Kepler does not
offer such an explanation but he is well aware of this
effect as one way by which white light (the white
noon day sun) can be transformed into colors (the
red setting sun).
Note 23 (Thesis 27)
Theories of the rainbow have long been a topic of
interest. Aristotle discussed the rainbow in terms of
the reflection of light; in the middle ages Grosseteste
and others interpreted it as a refraction phenomenon;
11I
and as late as the beginning of the twentieth century
it served as a doctoral dissertation topic for the
physicist Debeye.
Kepler here is discussing the colors of the half of
the rainbow referred to in the third sentence of this
Thesis as the class due to "refraction" (refractione).
Here, however, he attributes it to "reflection" (reflexionis). Perhaps he simply anticipates the "rainbow-reflecting surface" analogy that is to follow
(see Note 24). With either term, reflection or refraction, problems can be posed. If he does intend to
attribute this half of the rainbow to "reflection," then
the refractive properties to follow are not explained
by the rainbow but rather must be used to explain
it. If he does intend to attribute this half of the
rainbow to "refraction," then the result can demonstrate, by analogy, the reflective properties of surfaces.
Moreover, the portion of the prismatic colors that
would arise from refraction appear in the order given:
green, blue, and purple. Why, however, does he
attribute only half of the spectrum to refraction? Why
does refraction not also account for the yellow and red
half of the rainbow that were described as being due
to obfuscation (see Note 22) ? Boyer says, "Kepler
here seems to use the term refraction in the Aristotelian sense of reflection." [Boyer, 1950: p. 362]
Note 24 (Thesis 27)
Here an analogy is proposed between reflecting
surfaces and the rainbow with its two classes of
colors, one a product of (due to) absorption and the
other a product of (due to) refraction (reflection?).
The ability of a surface to reflect is derived from the
colors in the rainbow: the best reflector is a bright
surface and corresponds to the bright center of the
rainbow, which although it is not seen to be white,
nevertheless corresponds to white (see Note 21) ; second are surfaces corresponding to the next color on
either side of the center (yellow and green); third
in ability to reflect is the next pair (red and blue);
fourth is the next pair (purple and dusky); and last
is the black surface corresponding to black at either
extreme.
The Traditional
Prismatic
Colors
Kepler's
Description
of the Rainbow
Black
Red
Orange
Yellow
Green
Blue
Violet
Absorption
Refraction
usk
Red
Yellow
(White)
(WhitePi
Green
i
I
I
-
Reflecting
Pairs
Bluea
Purple+-Black
Note 25 (Thesis 28)
The color of the planets may be described in general
terms as follows: Saturn is dull yellow, Jupiter has
112
BRUCE BRACKENRIDGE
irregular bands of yellow and bluish or brownish grey,
Mars is ocher or greyish red, Venus is slightly yellow, and Mercury is copper-hued.
Note 26 (Thesis 32)
When discussing the ability of the sun to heat
(Thesis 9), we were told that it "warms more when
it is high than when it is low." In that instance
"high and low" referred to the angle the sun's rays
make at noon (see notes 13 through 16). In this
case "high" and "low" appear to refer to something
else, since for planets, "the greater angle at which they
are seen (i.e., low) so much more heat do they give."
One possible explanation might be that "low" refers to a planet that is close to the earth and hence
able to heat more, while "high" refers to a more distant planet. Consider the following sketch of the sun
and earth with Mars shown in two positions, conjunction and opposition.
Mars
For a Large Angle
"low" = near
For a Small Angle
"high"= far away
The difficulty in this description is that for either
near or far, the angle subtended by the planet is so
small as to defy comparison except in the abstract (i.e.,
it would be difficult to observe a variation with the
naked eye).
The final sentence, "But the power that is increased
by height has another cause," may well refer to the
geometric cause, that of aspects, to follow in section
two.
Note 27 (Thesis 33)
The sun enters into Cancer on the summer solstice.
Hence the time of elevation, nature of the atmosphere,
and the angle of obliquity all conspire to increase the
effect [see Theses 3-11 and Notes 13-16].
[PROC. AMER. PHIL. SOC.
SECTION TWO
Note 28 (Thesis 36)
A geometric angle is one that can be constructed
with a straight edge and compass. For example, a 60?
angle can be formed by generating an equilateral triangle and then bisecting or doubling as often as desired. Or, a 180? angle (a straight line) can be
bisected into a 90? angle and thence into a 450? angle,
etc. One can also construct a pentagon and thus get
multiples of angles of 72?. A harmonic angle is one
that is related to eight harmonic ratios of motion (to
be discussed in Thesis 38 and Note 30). Specifically,
it is one of the eight aspects Kepler employs in his
predictions (0?, 36?, 600, 72?, 90?, 120?, 135 , and
180?).
Note 29 (Thesis 37)
The full title of this work is the Precursor of
Cosmographic Dissertations or the Cosmographic
Mystery, and it is Kepler's first great work, published
in 1596. Although the opening chapter sets forth
very strongly and clearly Kepler's reasons for abandoning the Ptolemaic system in favor of the Copernican system, the major importance of the work is
its attempt to provide the first step in revealing the
universal harmony that Kepler was convinced existed
in planetary structure. What Kepler sought throughout his entire professional life was to discover the geometrical laws that were involved in the distribution
and motion of the planets. He is now best remembered
for his three laws of planetary motion, perhaps because
it is this portion of his work that was of interest to
Newton in the opening section of the Principia and
hence of interest to eighteenth and nineteenth century
physicists. In any event, Kepler himself takes as much
if not more pride in the order revealed in this work,
The Cosmographic Mystery, and in his later work, The
Harmonies of The World, than in his now famous
three laws of motion (which do not appear explicitly
under that title but are distributed throughout his
work on Mars in 1609 and in his later works).
The specific problem that he addresses in the
Cosmographic Mystery is that of the location and
number of the planets. Why are there only five
planets and why are their relative orbits as they are?
The solution, he reports, came to him during a lecture
while he was drawing a figure of the cycles of the
great conjunction of planets. There are only five regular solids-three dimensional figures with identical
faces that all join at the same angle: e.g., a cube-and
five intervals between the six celestial spheres. Kepler
envisioned a system of spheres circumscribed and
inscribed about the regular solids. Such a system has
the correct number of orbits and could be tested for
the relative size of the orbits. Employing the values
VOL. 123, NO. 2, 1979]
KEPLER ON ASTROLOGY
for the radii of the planetary spheres given by Copernicus, Kepler found that a "reasonable" fit could be
made between the spheres and the regular solids in the
following order: Saturn, cube, Jupiter, tetrahedron,
Mars, dodechedron, the earth, icosahedron, Venus,
octahedron, Mercury. The data fit is close enough to
be suggestive but imperfect enough to require further
effort. Unlike his "three laws of motion," improved
data tended to discount this law of planetary packing. In the ninth chapter of the work he derives
the astrological qualities of the five planets from the
nature of the five solids.
Note 30 (Thesis 37)
In 1619 Kepler published under the title The Harmonies of the World a work that was in effect the
sequel of his CosnmographicMystery (see Note 29).
Now, however, he had Tycho's very accurate data and
it was clear that the construction of the six planetary
spheres from the five regular solids was at best
approximate. Also, Kepler had analyzed the data
for the motion of Mars as well as for the spacing of
the planets, and in 1609 in The New Astronomy he
had derived the elliptical orbit and equal area laws:
the two relationships now referred to as Kepler's
first and second laws. In the Harmonies of the World
the data are further analyzed and the third law
emerges: the square of the period of a planet about
the sun is proportional to the cube of the mean
distance from the sun. The work, however, contains
much more. It is a hymn to geometry; God the
Creator is the Geometer and speaks in the universal
language of geometry; the heavens abound in harmony
expressed in planetary motion and positions that can
be recited and revealed in the harmonies of music.
Each planet has its own range of notes derived from
the ratio of diurnal arcs at aphelion and perihelion.
Thus, on the one hand, Mercury, with its great
eccentricity, has a wide range of notes. The earth,
on the other hand, with an almost circular orbit, is
restricted to sing simply mi, fa, mi. Such a song
is nevertheless consistent with Kepler's view of this
demanding world: "The Earth sings MI, FA, MI, so
that you may infer even from the syllables that in
this domicile MIsery and FAmine obtain." [Kepler,
1939: p. 1040.]
In particular, Kepler must find the correct index of
celestial motion in which to express the innate harmonies, i.e., the eight harmonic ratios of motion. He
considers five options, including the distances from
the sun and the periodic times, but concludes that it
is the diurnal arcs of the planets at perihelion and
aphelion, as seen from the sun, that is the correct
factor. Tables of these arcs are constructed from
Tycho's data, and ratios are taken from all possible
combinations (Jupiter at perihelion to Saturn at
113
aphelion, etc.). The test that these ratios must pass
in order to be adjudged correct is that they prove
to be consonant and that the single consonances
(ratios) do not "stand so separate that they have no
kinship with the rest." In fact the ratios must all
join together "in one octave of thenl which embraces
the rest in power . . . in such a way that there would
be a [musical] scale." [Kepler, 1939: p. 1035.]
Such a scale is found to exist and although various
ratios have to be transposed two or three octaves to
overlap, success is assured and the fundamental number of ratios of motion is set at eight, to conform to
the octave.
This correspondence between celestial motion and
musical scales does not come as a surprise to Kepler,
for as he says "Accordingly you won't wonder any
more that the very excellent order of sounds or
pitches in a musical system or scale has been set
up by men, since you see that they are doing nothing
else in this business except to play the apes of God
the Creator and to act out, as it were a certain drama
of the ordination of the celestial movements." [Kepler, 1939: p. 1038]
Note 31 (Thesis 38)
When the two luminaries, two planets, or a planet
and a luminary are in the same angular position aspect
in the zodiac, they are said to be in Conjunction:
i.e., their angular difference is zero. When they are
on opposite sides of the earth, their angular positions
in the zodiac differ by 180? and they are said to be in
Opposition. In Quadrature, Trine, and Sextile the
angular positions in the zodiac differ by 90?, 120?,
and 60? respectively. These are the five aspects that
have traditionally been employed by astrologers. The
three additional aspects added by Kepler are quintile,
a fifth part, or 72?; biquintile, a half of quintile or 36?;
and sesquiquadrature, one and a half of quadrature,
or 135?.
Kepler claims that "reason led" him to make the
addition and that "many experiences have since confirmed the choice." The "experiences" are obviously
successful predictions made on the basis of the new
aspects. [See, for example, the predictions for
January in Thesis 52.] The "reason" that led him to
add "three more" aspects to the traditional five evolved
from his long time concern with geometry, aspects,
and muscial consonance. As was made manifestly
clear in all his work (see Note 30), geometry was
for Kepler the key to understanding. It was revealed in all of God's work, astronomical, astrological, or musical.
In music, the beauty and fullness of geometry was
most clearly demonstrated in the consonances or
harmonies: the fundamental rates of notes that produce "harmonic" or "pleasing" sounds. These funda-
114
BRUCE BRACKENRIDGE
mental ratios have had different values at different
times and in different cultures. For the Pythagoreans,
the fourth (4: 3) was the smallest consonance.
According to Ptolemy the intervals could be ranked
in three categories of consonance: "the octave and
double octave are most satisfying to the human ear;
the fourth, fifth, eleventh, and twelfth next; the last
group includes the tone, the thirds, and the sixths."
(Bowden, 1974) p. 118. For Kepler, however, the
fundamental musical ratios were those of the "just"
intonation of the renaissance: 2:1 (octave), 3:2
(fifth), 4:3 (fourth), 6: 5 (minor third), 5:4 (major third), 5:3 (major sixth), and 8:5 (minor
sixth).
In astrology, the beauty and fullness of geometry
was most clearly demonstrated in the power of
planetary aspects or juxtapositions. An aspect is the
angle between two celestial objects. Thus when Mars
and Jupiter are separated by 120? along the zodiac
they are said to be in trine: one third of a full circle.
But there is an unlimited number of such angles
and the astrologer had to select the "correct" ones to
use in his prognosis. For Kepler, it was a correspondence between the major consonances and the
major aspects that supplied the "reason" for his selection. This idea was not new with Kepler; rather it
was the emphasis placed on aspects and their relationship with music that distinguished him from Ptolemy,
for example. For Ptolemy, "tuning entered into the
aspect theory only marginally; it depended mainly on
the common ground of the Pythagorean and Ptolemaic
octave, fourth, fifth, and twelfth. . . . The general
procedure consisted in generating ratios from the
aspects by comparing the arcs of circle so cut off and
then correlating these with harmonic ratios." (Bowden, 1974: p. 118.) Thus when two celestial objects
are said to be in trine, the angle between them is
120? and the arc cut off is 240?. Thus its ratios
with the full circle is 360? to 240? or 3: 2 and its corFor Keprespondence in music is to a fifth (3:2).
ler, however, the consonances were those of the "just"
intonation, and just as "the ear is stimulated by harmony [consonances] . . . so the earth is stimulated
through the geometric concourse of vegetating rays
[aspects]" Thesis 43. Thus since there were seven
consonances in the "just" scale, so there must be seven
aspects in the astrological system. In the Mysterium
Cosmographicum Kepler states:
[PROC. AMER. PHIL. SOC.
monic ratios of the just scale as follows: (Bowden,
1974: p. 153.)
OPPOSITION
2:1 OCTAVE
TRINE 3:2
QUARTILE
4:3 FOURTH
SEXTILE
6:5 MINOR THIRD
The fifth traditional aspect is conjunction and would
correspond to a ratio of 1: 1 or perhaps unison. The
three new aspects suggested by Kepler are related to
the three remaining harmonic ratios as follows: (Bowden, 1974: p. 153.)
5:4
QUINTILE
MAJOR THIRD
5:3
BIQUINTILE
MAJORSIXTH
Therefore since all four harmonies agree with their
aspects, and in fact three harmonies remain in music, I
have a suspicionthat it shouldnot be neglectedin judging
of nativities if the planets are 72 or 144 or 135 degrees
apart, especiallysince I see that one of the imperfectshas
its aspect. (Bowden, 1974: p. 119.)
Thus the four traditional aspects employed by
astrologers are related by Kepler to four of the har-
FIFTH
SESQUAQUADRATE
8:5 MINOR SIXTH
VOL. 123, NO. 2, 1979]
KEPLER ON ASTROLOGY
However the events of 1602 supported his new
aspects, they failed in the long run. As Bowden states:
This beautiful unitary structure was destroyed by the
meteorological research he had advocated. Several of
Kepler's contemporariesset about making weather observationsto test new aspects. Unconstrainedby Kepler's
harmonic predilections, his followers were more openminded in finding correlations between angles and the
weather. At least in some cases this freedomwas owing
to a misprint. According to Kepler's account of 45? instead of 135?, "sequadrum,"instead of "sesquadrum,"
thinking "semi"instead of "sesqua." Kepler credited his
old teacher Mastlin with suggesting the possibility of aspects beyond the three Kepler had added. In late 1607
Kepler convertedto this conclusion. The sesquaquadrate
did not correlate at all well with the weather, but the
"semisextile' (30?) did. This was the long avoided
separationof one sign, which had little to do with music.
(Bowden, 1974: pp. 121, 122.)
Note 32 (Thesis 42)
115
ensued with great loss of life. His army was defeated and retreated in great disorder.
Note 35 (Thesis 71)
The wedding was that of Henry Bourbon, King of
Navarre, and Margaret Valais, the sister of Charles
IX of France. It was at this time that the massacre
of the Huguenots occurred on St. Bartholomew's Day
(August 23-24, 1572).
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HALL. 1959. "Tycho Brahe's
BOAS,MARIEand A. RUPERT
System of the World" Occasional Notes of the Royal
Society 3: 21 (1959) : pp. 257-263.
CARL. 1950. "Kepler's Explanation of the Rainbow."
BOYER,
American Journal of Physics 17: pp. 360-366.
1975. Ancient Astrology Theory and Prac-
BRAM, JEAN.
tice (Park Ridge).
A translation of Matheseos Libri
VIII by Firmicus Maternus (also contains an extensive bibliography on ancient and modern astrological
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in possession of a soul. There are, however, several CASPER, MAX. 1959. Kepler (London). Translated by C. D.
Hellman.
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of thought), sentience (capable of sensation), mobil- CONINGTON, JOHN. 1893. The Satires of A. Persilis Flaccus
(Oxford).
ity (capable of spatial movement and rest), and the COOPLAND,
GEORGE.1952. Nicole Oresme and the Astrologer
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(Liverpool).
Plants have only the faculty of nutrition. All ani- DALES, R. C. 1973. The Scientific Achievement of the
Middle Ages (Philadelphia).
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DOREY,
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Discoveries and Opinions of
there is a small fraction of living things that possess
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in addition to sentience and nutrition the faculty for DREYER,J. L. E. 1963. Tycho Brahe, a Picture of Scientific
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