Mind and Chance

Abstract

Much discussed but still unresolved is whether a subject's internal physical structure is a sufficient condition for his beliefs and desires. The question has sometimes been expressed as a question about microstructurally identical Doppelgänger. Imagine two subjects who are identical right down to the ions traversing the synapses. Their senses are stimulated in all the same ways, their bodies execute the same motions, and identical physical events mediate between the sensory inputs and the behavioral outputs. Must they have the very same beliefs and desires? Let us call the thesis that they must, internalism. The internalist may hold that a physical similarity less complete than this will also guarantee identity in beliefs and desires, but certainly, he holds, perfect identity of internal physical histories will suffice.Internalism will be opposed by those who sense that the nature of mentality is closely tied to the nature of explanation in terms of mental states and that in explaining a subject's behavior we cannot abstract, even in principle, from the character of the environment in which the subject is embedded. This essay offers a partial articulation of this point of view and shows how it conflicts with internalism. A consequence of the view to be described is that our attributions of belief must reflect the probabilistic regularities in the subject's environment. As we shall see, this consequence conflicts with internalism in two ways. The first conflict turns on the fact that there is no limit on the possible variety of such regularities. The second conflict turns on the fact that two subjects might by chance have the same micro-structural history though different probabilistic regularities obtain in their respective environments.