1 The Birth of Science - MSRI

350 11. The Age-Long Recovery
the new psychology of perception, founded on the essential need for active
subject participation, or assent (©) in the terminology of
Chrysippus. 189
German-language authors were at the forefront of all these advances:
they came from the same culture that almost single-handedly made classical
philology into the rich structure it had become by the close of the
nineteenth century. Among the results that arose at the turn of the twentieth
century from the fecund interaction of classical philology, history of
science and epistemology was the underdetermination of scientific theories:
that is, the rediscovery of the possibility of using different theories to
explain the same phenomena. Henri Poincaré and Pierre Duhem (scientist,
epistemologist and historian of ancient science) played a key role in
this realization. Duhem denied, for example, the validity of so-called crucial
experiments for “confirming” a theory, thus turning on its head their
supposed absence from ancient science. 190 The work of recovery seemed
finally to have come to a conclusion in the methodological dimension as
well.
In the following decades historians of science followed paths that diverged
ever further from those of scientists and epistemologists. The study
of ancient thought became the province of a few specialists, who talked
but little with philosophers and scientists. It was then that the minimalist
views that we have discussed took hold. 190a
At the same time, an enormous increase in the range of observed phenomena
demanded the creation of new scientific theories, toward which
no light could come from reading Archimedes nor yet from browsing
through all of Plutarch. Small-scale physics proved impossible to describe
via classical mechanics: its phenomena do not conform either to the theory
of particles or to that of waves. It was obviously necessary to build another
theory, but the way in which that theory arose and developed shows how
serious was the loss of the sure guide that had sustained us until then.
Instead of proposing a third scientific theory, scientists such as de Broglie
and Bohr postulated “particle-wave duality” and the “complementarity
principle”. Faced with the inapplicability of two mutually incompatible
189 See pages 151 and 185. The new psychology was born thanks to Franz Brentano (1838–1917),
whose two main interests were psychology and the history of ancient philosophy.
190 See especially [Duhem: TP] and [Duhem: SPh]. Duhem regarded many ancient scientists (not
excluding the imperial period) as conventionalists, and his position has been sternly criticized
(on valid grounds in many specific cases; see in particular [Lloyd], chapter 11). But we should
not forget that conventionalism arose in modern science thanks to intellectuals who, like Duhem,
found it in ancient sources.
190a See Section 9.1.
Revision: 1.11 Date: 2003/01/06 07:48:20