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Starry Messenger (1610)
1. What were Galileo’s telescopic
observations?
2. Did these observations prove the
Copernican system?
3. How did he use them to attack &
undermine Aristotelianism?
4. Were his troubles with the
Church simply “science” versus
“religion”?
SIDEREAL MESSENGER
unfolding great and very wonderful sights
and displaying to the gaze of everyone,
but especially philosophers and astronomers,
the things that were observed by
GALILEO GALILEI
Florentine patrician and public mathematician
of the University of Padua,
with the help of a spyglass lately devised by him,
about the face of the Moon, countless fixed stars,
but especially about four planets
flying around the star of Jupiter at unequal intervals
and periods with wonderful swiftness;
which, unknown by anyone until this day,
the first author detected recently and
decided to name
MEDICEAN STARS
Most Serene Cosimo, [when] I
discovered these stars . . . I
decided by the highest right to
adorn them with the very august
name of Your family. . . For to be
silent about Your Most Serene
Highness’s ancestors to whose
eternal glory the monuments of all
histories testify, Your virtue alone,
Great Hero, can, by Your name,
impart immortality to these stars .
..
Most Merciful Prince,
acknowledge this particular glory
reserved for You by the stars and
enjoy. . . divine blessings carried
down to You. . . from the Maker
and Ruler of Stars, God.
“[The moon] is not robed in a smooth and polished
surface . . . [but is] rough and uneven, covered
everywhere, just like the earth’s surface, with huge
prominences, deep valleys, and chasms.”
“You will behold through the
telescope a host of other stars,
which escape the unassisted sight,
so numerous as to be beyond
belief.”
“I have observed the nature and
the material of the Milky Way . . .
Upon whatever part of it the
telescope is directed, a vast crowd
of stars is immediately presented
to view. Many of them are rather
large and quite bright, while the
number of smaller ones is quite
beyond calculation.”
“[Now] we have not just one
planet rotating about another
while both run through a great
orbit around the sun; our own
eyes show us four stars which
wander around Jupiter as does the
moon around the earth, while
altogether trace out a grand
revolution about the sun in the
space of twelve years.”
Frontispiece:
Dialogue on the Two
Chief World Systems
(1632)
Characters:
Salviati
Sagredo
Simplicio
I say that it seems prudent that Your Paternity and Mr.
Galileo are proceeding prudently by limiting yourselves to
speaking suppositionally and not absolutely, as I have
always believed that Copernicus spoke. For there is no
danger in saying that, by assuming the earth moves and
the sun stands still, one saves all the appearances better
than by postulating eccentrics and epicycles; and that is
sufficient for the mathematician. However, it is different to
want to affirm that in reality the sun is at the center of
the world. . . and the earth. . . revolves with great
speed around the sun; this is a very dangerous thing,
likely not only to irritate all scholastic philosophers and
theologians, but also to harm the Holy Faith by rendering
Holy Scripture false. . .
Cardinal Bellarmine, Letter to Father Foscarini, 1615
[In] order that this opinion may not creep any further to the
prejudice of Catholic truth, the Congregation has decided
that the books by Nicolaus Copernicus and Diego de
Zuñiga be suspended until corrected; and that all other
books which teach the same be likewise prohibited. . .
Decree of the Index of Prohibited Books, 1616
I would be greatly inclined to agree that the cause of tides
could reside in some motion of the basins containing
seawater; thus, attributing some motion to the terrestrial
globe, the movements of the sea might originate from it. . .
Galileo, Discourse on the Tides, 1616
Salviati: . . . I say that human wisdom understands some
propositions as perfectly and is as absolutely certain
thereof, as Nature herself; and such are the pure
mathematical sciences, to wit, Geometry and Arithmetic.
In these Divine Wisdom knows infinitely more propositions,
because it knows them all; but I believe that the
knowledge of those few comprehended by human
understanding equals the Divine, as to objective
certainty . . .
Simplicio: This seems to me a very bold and rash
expression.
First Day, Dialogue
Simplicio: But in case we should give up Aristotle, who is
to be our guide in philosophy? Name you some author.
Salviati: We need a guide in unknown and uncouth parts,
but in clear thoroughfares, and in open plains, only the
blind stand in need of a leader . . . But he who has eyes
in his head and in his mind has to use these for his
guide. Yet mistake me not. . . I commend the reading and
diligent study of [Aristotle] and only blame the servilely
giving one’s self up a slave to him, so as blindly to
subscribe to whatever he delivers. . .
Second Day, Dialogue
[Many] times in the work there is a lack of and deviation
from hypothesis, either by asserting absolutely the earth's
motion and the sun's immobility, or by characterizing the
supporting arguments as demonstrative and necessary, or
by treating the negative side as impossible . . .
...
[Galileo] wrongly asserts and declares a certain equality
between the human and the divine intellect in the
understanding of geometrical matters . . .
Report on the Dialogue, 1632
Although at the beginning of his book Galileo claims to want
to deal with the earth's motion as a hypothesis, in the course
of his Dialogue he puts the hypothesis aside and proves its
motion absolutely, using unconditional arguments . . .
Report on the Dialogue, 1633
I must altogether abandon the false opinion that the Sun
is the center of the world and immovable and that the
Earth is not the center of the world and moves and that I
must not hold, defend, or teach in any way
whatsoever, verbally or in writing, the said false
doctrine, and after it had been notified to me that the
said doctrine was contrary to Holy Scripture- I wrote and
printed a book [Dialogue] in which I discuss this new
doctrine already condemned and adduce arguments of
great cogency in its favor without presenting any solution
of these, I have been pronounced by the Holy Office to
be vehemently suspected of heresy. . . I, Galileo
Galilei, have abjured as above with my own hand.
Galileo’s recantation, 1633