Possessing a concept according to the philosophy of Peacocke

Christopher Peacocke defends a sophisticated version of Conceptual Role The ory. For him, the nature of a concept is completely determined by an accoun t of what it is to possess that concept. The possession conditions he puts forward rest on the notion of primitively compelling transitions, or, more recently, on the idea of implicit conceptions. I show that his account is c ircular and appeals to a dubious distinction between constitutive transitio ns (or conceptions) and transitions (or conceptions) that depend on factual beliefs. I also point out that his possession conditions violate the Publi city Constraint; and finally, I raise doubts about the psychological realit y of primitively compelling transitions and implicit conceptions.