Popper: “Falsifiability is the criterion” Lecture updated!

1. 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!

2. Popper: “Falsifiability is the criterion” • Falsifiability: • 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 false. • 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 “pseudo-scientific”

3. 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?

4. Popper: “Falsifiability is the criterion” • His targets: • Adlerian psychology • 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

5. Popper: “Falsifiability is the criterion” • His targets: • Adlerian psychology • 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 behaves!

6. 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 justone failed experiment or prediction, by just one observation.

7. If H, then I I ------------------ H Logic of confirmation: Affirming the consequent Deductively invalid If H, then I Not I ------------------ Not H Logic of falsification Modus Tollens Deductively valid. The logic of confirmation vs. the logic of falsification

8. 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.

9. 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.

10. 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 heads) • 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

11. 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 view. • 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

12. Eddington’s experiment • A reconstruction of what Eddington’s photographs demonstrated:

13. 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 bold…

14. Falsifiability • 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…)

15. Things we will later consider… • The difference between a theory actually being un-falsifiable, 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 encountered? • 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)