As has been recognized at least since the time of the British Empiricists, theories of concepts and of concept acquisition are mutually constraining. Dr. Carey reviews the current state of the art on concept acquisition to argue for three theses: I. Some conceptual representations are innate, embedded in systems of core cognition. II. Most conceptual representations are qualitatively different from those in core cognition, such that conceptual development involves interesting discontinuities. III. One learning mechanism capable of achieving conceptual discontinuities is Quinian bootstrapping. Dr. Carey will illustrate what these theses come to, and the evidence for them, through a case study of the origin of representations of natural number. And she will draw some implications for a theory of concepts from her picture of conceptual development.nt.