How to Perform a Reduction

Abstract

A reductionist is an imperialist in the service of physics. His ideal is that of a unified science. At bottom everything ontologically is physical. Everything is also ultimately determined by what happens at the lowest physical or micro-physical level.' Finally everything is explicable in terms of physics. The reductionist has his enemies. He rejects and wishes to root out and extirpate doctrines of emergence, vitalism, holism, and dualism. New properties cannot spontaneously emerge in complex systems without being explicable in terms of the structure and components of the system. There is no life force besides the forces of physics. Life is ultimately a physico-chemical process. If any whole is greater in any sense than the sum of its parts then this is quite explicable in terms of the nature of its components and the way they are put together. Finally, there are no ghosts, spirits or souls. Contemporary philosophy and philosophy of mind in particular, is, by and large, deeply sympathetic to the reductionist's crusade. However, the orthodoxy is to reject reductionism and be content with the feeble, milk and water pabulum of supervenience. The reason for this, I wish to argue, is the very excellence of that locus classicus on reduction Chapter 11 of Ernest Nagel's The Structure of Science.2 Nagel slew the reductionist's dragons using the account of explanation which was orthodox amongst those working in the footsteps of the Vienna Circle. The paradigm of explanation was hypothetico-deductive. Deductive explanation was the norm in classical mechanics in the explanation of individual phenomena. In reduction, the explanation of one science by another, the laws of the secondary science were explained by the laws of the primary science through being deducible from them with the assistance of bridge laws. Nagel's mistake, I hold, was believing that everything should be explained by physics in the way things are explained within