FALSIFIABILITY IS THE HEART OF SCIENCE KARL POPPER FALSIFIABILITY IS THE HEART OF SCIENCE

Sir KARL POPPER 1902-1994 Hume is right: we never get beyond conjectures. “Darwinian” view of human “knowledge”: PS1TT1 EE1PS2…

PROBLEM OF THE CRITERION (264, theme of whole essay) Problem: what distinguishes science from non-science or pseudo-science? Lots of theories in political “science” (e.g., Marx, Spengler, Nazism), psychoanalysis (Freud, Adler, Jung), claim to be scientific. ARE THEY? Popper’s experience in Adler’s clinic (p. 265). Everything is consistent with, hence corroborates or confirms his theory.

NON-SCIENCE IS UNFALSIFIABLE. NONSCIENTIFIC THEORY Marx, Spengler, Hitler, Freud, Adler: Everything confirms their theories, nothing falsifies them. N.B.: not just every actual thing, but every conceivable thing. NON-SCIENCE IS UNFALSIFIABLE.

SCIENTIFIC THEORY Newton, Einstein: most conceivable things falsify their theories: N.B.: though no actual thing does Example: A body has to fall (orbit, etc.) with a precise acceleration (velocity, etc), or else theory is false. N.B.: though in fact theory is not falsified.

PROBLEM OF THE CRITERION Observation: Marx’s, Freud’s, Adler’s, etc., theories take no risk, but Einstein’s is risky (= falsifiable). So, maybe: Falsifiability is the criterion of science

FALSIFIABILITY 1 (P’s summary of numbered list, p. 266) Popper accepts above solution: Falsifiability is the criterion of science Falsifiability =DEF the logical possibility of being proven false by observation =DEF can conceive of such proof without self-contradiction

FALSIFIABILITY 2 Falsification of scientific claim is logically valid: T  O ~ O_____ Thus ~ T T=Theory is true O=Observation implied by theory occurs. [Recall Salmon, invalidity of scientific confirmation: T  O; O; Thus T.]

FALSIFIABILITY [3] Falsifiable or not? a) Unicorns do not exist. Assume: unicorns are not invisible b) Unicorns exist. c) 3 x 7 = 21 d) Hitler never once wore mismatched socks. e) Dinosaurs once roamed the Earth

SCIENTIFIC THEORIES ARE PROHIBITIONS [explanation of Popper’s item #3, p. 266] In a state of perfect ignorance, all things are possible so far as we can tell. E.g., F=ma or F=2ma or F=3ma or… Knowledge rules out some possibilities OR: scientific theories are constrained by observational data

THE SCIENTIFIC ATTITUDE [explanation of Popper’s item #5, p. 266] “Genuine test” is defined in terms of attempts to falsify. Theories can be protected from the evidence by qualifications, promises, etc. E.g.: Is the theory of global warming falsified by the years of cooling?

POPPER’S “SOLUTION” OF HUME’S PROBLEM OF INDUCTION i) Deduction is the only logic; there is no inductive logic. ii) Theory of rationality: accept boldest unfalsified falsifiable theory bold=risky=high content Timid: the robin will fly south in the fall Bold: the robin will fly south on 26 Oct. Bolder: …26 Oct. at 1:23 p.m., SSW,…