Stathis Psillos, Scientific Realism: How Science tracks Truth, 1999 — Chapter 5, ‘resisting the pessimistic induction’

Psillos deconstructs and counters one major challenge to realist understandings of scientific theories/knowledge.

Psillos’ chosen opponent is Laudan. Laudan argues that since past theories now ‘abandoned’ by current science were once empirically successful for a considerable period, the ties that realists make between empiricism (observation through experiment), truth, and the longevity of a scientific theory (how long a theory is believed by scientists to explain the world) is undermined.

Laudan argues there is no reason to accept ‘realist’s warrant’ that :

‘today’s theories, including even those which have passed an impressive array of tests, can thereby warrantedly be taken to be .. “cutting the world at its joints”’[knowing the world for what it really is]

Laudan’s argument is formalised by Psillos as:

(A) Currently successful theories are approximately true

(B) If currently successful theories are truth-like, then past theories cannot have been true

(C) These characteristically false theories were, nonetheless, empirically successful

Psillos’ defence of realism relies on the idea that past theories have been explanatorily successful, rather than just empirically successful (contra Laudan).

Successful explanation is defined by Psillos as successful prediction. A theory that successfully explains is a theory which predicts phenomena not used in the construction of that theory and unknown before the construction of that theory.

To meet Laudan’s attack of realism fully, Psillos tries to

Identify the theoretical constituents of past genuine [explanatorily] successful theories that made essential contributions to their successes and
show that these constituents..have been retained in subsequent theories of the same domain

Psillos argues that there are several case studies that meet these two criteria: the stages in the development of caloric heat theory, and the 19th century optical ether theories.

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