Abstract
In this lecture on concepts and their persistence through time, we begin by recalling the classical theory (now discredited) that the content of a concept is a "definition". The definition associated with the concept (and constituting its content) provides a criterion for the concept's application, and thus determines its "extension": everything that satisfies the definition falls under the concept. The associated definition also makes it possible to individualize the concept, i.e. to distinguish it from other concepts.
After recalling the reasons for rejecting the classical theory, and generally characterizing the theories that have replaced it, we radically challenge the idea that the content of a concept (1) determines its extension, and (2) makes it possible to individualize the concept (by distinguishing it from all others). The idea that the content of a concept determines its extension has been largely abandoned by philosophers in favor of the externalist thesis that it is the environment in which the concept is deployed or acquired that determines its reference (what the concept relates to). With regard to individualization, the specific theme of this lecture, three options are presented and discussed. According to inferentialisttheory , two concepts are the same if they have the same content, i.e. if they are associated with the same "conception". This theory is incompatible with the necessary stability of concepts over time. According to the referentialist theory , two concepts are the same if they have the same reference (if they refer to the same reality). This theory is opposed by the "Fregéan cases". Finally, according to the véhicularist theory , the one I defend, the conception (the content of the concept) can vary without affecting the identity of the concept, because the concept is individualized not by its content but by its vehicle (the mental file that houses the conception but persists when it changes).