The Non-circularity Constraint: Peacocke vs. Peacocke

According to the view that Peacocke elaborates in A Study of Concepts (1992), a concept can be individuated by providing the conditions a thinker must satisfy in order to possess that concept. Hence, possessions conditions for concepts should be specifiable in a way that respects a noncircularity constraint. In a more recent paper "Implicit Conceptions, Understanding and Rationality" (1998a) Peacocke argues against his former view, in the light of the phenomenon of rationally accepting principles which do not follow from what the thinker antecedently accepts. In this paper I defend the view of the book from his more recent criticisms, claiming that the noncircularity constraint should be respected, and that Peacocke's more recent insights could be accommodated in the framework of his former theory of concepts.