A theory of conceptual development must provide an account of the innate representational repertoire, must characterize how these initial representations differ from the adult state, and must provide an account of the processes that transform the initial into mature representations. In The Origin of Concepts (Carey 2009), I defend three theses: (1) the initial state includes rich conceptual representations, (2) nonetheless, there are radical discontinuities between early and later developing conceptual systems, (3) Quinean bootstrapping is one learning mechanism that underlies the creation of new representational resources, enabling such discontinuity. Here I argue that the theory of conceptual development developed in The Origin of Concepts constrains our theories of concepts themselves, and addresses two of Fodor’s challenges to cognitive science; namely, to show how learning could possibly lead to an increase in expressive power and to defeat Mad Dog Nativism, the thesis that all concepts lexicalized as mono-morphemic words are innate. In response to Fodor, I show that, and how, new primitives in a language of thought can be learned, that there are easy routes and hard ones to doing so, and that characterizing the learning mechanisms in each illuminates how conceptual role partially determines conceptual content.
