Abstract:Many psychologists think that concepts should be understood on analogy with the terms of scientific theories, yet the significance of this claim has always been obscure. In this paper, I clarify the psychological content of the theory analogy, focusing on influential pieces by Susan Carey. Once plainly put, the analogy amounts to the view that a mental representation has its semantical properties by virtue of its role in a restricted knowledge structure. One of the commendable things about Carey's work is that, unlike many other psychologists who appeal to the theory analogy, she takes seriously the need to specify how these structures are constrained. At the same time, the constraints she offers are insufficient. Her account also faces challenges from recent work in the semantics of natural kind terms.