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Popper: “Falsifiability is the criterion”
Lecture updated!
Why reject verifiability?
By then (for reasons we will study shortly), scientists and
philosophers recognized that no empirical theory could
ever be proven.
This seemed to take any degree of certainty off the table
Moreover, according to Popper, “verifications” or
confirmations of a theory were, in many cases, all too easy
to come by.
‘Falsifiability’ is a criterion scientists often site… as do
their critics!
Popper: “Falsifiability is the criterion”
 Do be scientific, a claim, hypothesis, or theory
must be, in principle at least?, falsifiable
 It must rule out/prohibit some observable (in
principle?) object or event that, if observed, would
demonstrate the claim, hypothesis or theory is
 If a claim or theory is compatible with all and any
states of affairs, it is not falsifiable and thus not
scientific (or, as Popper claims” it is “pseudoscientific”
Popper: “Falsifiability is the criterion”
Exhibit A:
 In
court cases decided (in one instance) by the US
Supreme Court and by state supreme courts, first
“Creation Science” and, more recently, “Intelligent
Design” were banned from public schools on the
grounds that they were not falsifiable, thus not
scientific but rather religion (which can’t be taught in
public schools).
 Advocates of CS and ID then argued that evolutionary
theory isn’t falsifiable and, thus, not science!
BTW: is String Theory falsifiable?
Popper: “Falsifiability is the criterion”
His targets:
 Adlerian
 Freudian psychology
 Marxist theory
What they have in common:
 Their
advocates see confirmations everywhere
Where (I contend) they differ:
 The
first two may well be “unfalsifiable”
 The problem with Marxism (which was falsifiable) was
with its advocates, not the theory itself
Popper: “Falsifiability is the criterion”
His targets:
 Adlerian
 Freudian psychology
What renders them “unfalsifiable”?
 Not
the uncritical attitude of their advocates
 The second has a “protective belt” that effectively
repels all counter-evidence
 The first is simply compatible with any way an agent
Popper: “Falsifiability is the criterion”
Popper has logic on his side; for while no empirical
theory can be proven, any (genuinely) empirical
theory can be disproven and, at least in principle,
by just one failed experiment or prediction, by just
one observation.
The logic of confirmation vs. the logic of
If H, then I
2. I
Logic of confirmation:
Affirming the consequent
Deductively invalid
If H, then I
2. Not I
-----------------Not H
Logic of falsification
Modus Tollens
Deductively valid.
The Mind’s Big Bang
The Paleolithic period (or Old Stone Age) is the earliest
period of human development. Dating from about 2
million years ago, and ending in various places between
50,000 and 10,000 years ago, it is roughly co-extensive
with the geologic period known as the Pleistocene [some
would update timeline]
An epoch which was marked by continuous cooling,
which resulted in several ice ages. During the period,
hominids become increasingly advanced in terms of fire
and tool making, and modern humans emerge.
The Mind’s Big Bang
Evidence of Cro-Magnon humans (one of several varieties
of modern humans that lived during the period) indicates
they lived some 50,000-10,000 years ago. Anatomically
the same as today’s Homo sapiens and fossil remains,
graves, artifacts, and dwellings have been found
throughout Europe.
It is believed that their arrival in Europe, when they
encountered another hominid species, the Neanderthals,
resulted in the extinction of the latter.
In a recent article in “The Science Times,” it was
hypothesized that Cro-Magnons were so startled to be
confronted with another bi-pedal, tool using (and much
larger!) hominid, that they developed the practice of
designing beads that would identify them.
The Mind’s Big Bang
The discovery of decorative beads
Differences in the treatment that humans and Neanderthals provided
the dead
Cave paintings
Fossil evidence (particularly skulls) of differences between
Neanderthals and humans
Relatively quick innovations (in, for example, spears and spear
Migrations of early humans across Europe
Cave instruments and music
Biological changes in the brain
Comparison of humans and chimpanzees
The emergence and significance of language
Cultural forces overriding biological forces
Popper: “Falsifiability is the criterion”
Although it was unclear at the time whether Einstein’s
theory was true, it turns out to be scientific on Popper’s
Eddington’s experiment:
Einstein’s theories predicted that light, like material objects, is
subject to the gravitational “pull” of large objects
Hypothesis: light traveling from a star that is located “behind”
the sun from the perspective of the Earth should bend as it passes
the sun
A bold hypothesis and one that would take years to carry out.
Scientists had to wait for a solar eclipse so that a star’s light
would be visible
Eddington’s experiment
A reconstruction of what Eddington’s photographs
Eddington’s experiment
Again, it was not the confirmation of Relativity
that struck Popper, but its falsifiability and
boldness: even before Eddington’s experiment
confirmed it, scientists knew what would, in
principle, falsify the hypothesis: namely, not
observing the bending of the light traveling from
the star toward Earth.
 Moreover, confirmations of a theory should only
count as significant when the theory in question is
Marxism is rendered pseudo-scientific not
because the original theory was not falsifiable.
 Marx and Engel’s claims about upcoming
proletariat revolutions in capitalist societies were
falsifiable, and in most cases, falsified.
 But advocates of Marxism, in efforts to save the
theory from the falsifications, introduce Ad hoc
hypotheses to save it.
 Ad hoc: From the Latin “for this purpose” (in this
case, saving the theory…)
Things we will later consider…
The difference between a theory actually being unfalsifiable, by its nature or structure, and a theory’s
advocates resorting to ad hoc hypotheses to save it.
Isn’t it possible that a genuinely scientific theory will
be confirmed repeatedly and no counter-examples
The “in principle” caveat is important. “There is a
little red school house on the dark side of Jupiter” is
silly but falsifiable in principle.
How easy or straightforward is it to identify added
hypotheses that ARE ad hoc, but added hypotheses
that are NOT ad hoc (i.e., are defensible)