Virgil Whitmyer

Many models of the mind, both philosophical and psychological, invoke the mathematician's concept of isomorphism. Various theories posit that representation consists in isomorphism between a representation and that which it represents, that spatially distributed sensory states are realized in brain states to which they are isomorphic, or that psychological state spaces are realized in neural state spaces to which they are isomorphic. Among these theories, isomorphism is sometimes used as a methodological guide or constraint, and other times it plays a role in general philosophical accounts. The dissertation proposes a taxonomy of various uses of representation, and examines the usefulness of isomorphism for both the methodological and philosophical enterprises in theories of perception and certain theories of representation. I argue that isomorphism is not a useful guide to methodology, and probably cannot serve as a constraint on theories. Isomorphisms are too common, and some theories face Goodman-style worries about arcane isomorphisms between structures with non-natural properties. Many philosophical theories also require that isomorphism be constrained to be useful. I describe worries for theories of representation on which isomorphism is sufficient for representation. I argue that property realism is not a sufficient constraint to ground a theory of representation according to which isomorphism is sufficient for representation, and describe a stronger sort of realism. Finally I argue that philosophical claims that isomorphism is a necessary feature of representation are either trivially true or matters for empirical work to decide

In his 1995 book Colour vision (New York: Routledge), Evan Thompson proposes a new approach to the ontology of color according to which it is tied to the ecological dispositions-affordances described by J.J. Gibson and his followers. Thompson claims that a relational account of color is necessary in order to avoid the problems that go along with the dispute between subjectivists and objectivists about color, but he claims that the received view of perception does not allow a satisfactory relational account of color. Hence to avoid the problems of the subjectivist/objectivist dispute one must abandon the received view of perception. I describe an account which is similar to Thompson's, but which invokes instead the physical dispositional properties described by the received view. All of the distinguishing characteristics that Thompson claims separate his ecological dispositions from physical dispositions are in fact found in the physical dispositions appealed to by my proposed theory. Because my proposed theory is similar to subjectivism, Thompson's departure from the received view is not as radical as he claims. In a final section I describe the a posteriori manner in which a substantive departure from the received view must be carried out by describing an example of ecological experimentation