Reductionism and integrationism in Descartes’s biology

Barnaby Hutchins

Ghent University

This paper argues that Descartes’s theoretical claims about mechanism should be distinguished from his use of mechanism in biology: in his theoretical claims, Descartes is a strong reductionist, but in his biology, he is closer to what Darden and Craver (2009) have termed ‘integrationism’. As such, we find a philosophy of science in Descartes’s biology that is in contrast to his better-known explicit claims. The new mechanist literature has tended to see Descartes (along with the early-modern mechanical philosophy in general) as a forerunner of its own programme (e.g. Glennan 1996). Descartes is attractive to the new mechanists precisely because of his theoretical claims about both ontology and methodology. Ontologically, he commits himself to a material world that contains nothing more than corpuscles of extended substance in motion. Methodologically, he appears to commit himself to explanation of all natural phenomena in terms of nothing more than the ‘shape, size, position and motion of particles of matter’ (Principles of Philosophy: 4/187). As such, Descartes claims that everything that happens in the world is the product of miniature mechanisms made up of subvisible corpuscles. The apparent continuity between Descartes’s claims and the new mechanist approach, which holds that ‘the practice of science can be understood in terms of the discovery and description of mechanisms’ (Machamer et al. 2000: 2), is obvious and literal. However, Descartes’s claims commit him to a strong form of reductionism (down to the most basic ontological units) that the new mechanists generally reject (e.g., Machamer et al. 2000, Craver 2005 and 2007, Darden 2006, Bechtel 2007). Theurer (forthcoming) has gone so far as to propose that Descartes’s theoretical claims provide a model for reintroducing strong reduction to modern mechanism. Given that modern mechanism explicitly positions itself as an approach ‘grounded in the details of scientific practice’ (Machamer et al. 2000: 2), however, I argue that the appropriate point of comparison is Descartes’s practice of explanation in biology, and not his theoretical claims about ontology and methodology. I analyse Descartes’s accounts of the main bodily functions (the heartbeat, respiration, digestion, and muscular movement), and show that he avoids reduction down to basic ontological units. His explanations are in not given in terms of miniature corpuscular mechanisms. In fact, they rarely involve corpuscles at all. Rather, Descartes’s general approach is to integrate components from multiple explanatory levels. The heartbeat, for example, involves the behaviour of blood corpuscles, but that behaviour is determined by the relaxation of the heart as a whole (which itself is determined by the interaction between expanding blood and the ventricle walls, along with the entire circulatory system). Thus, Descartes’s approach to explanation in biology recognises, just as the new mechanists do, that an integrative approach provides a more ‘accurate understanding of the causal structures of [. . .] mechanisms’ (Darden and Craver 2009: 5) than reductionism of the kind he espouses in his theoretical claims.