Abstract: A concept in the psychological sense is the mental representation of a category, and a mental concept is the mental representation of a mental category or type, such as belief, desire, fear, or hunger. What are the vehicles of mental concepts and what are their contents? There is a proprietary internal code, the introspective code, which employs introspection-derived mental vehicles to represent mental categories. Introspection-based concepts bear some similarity to the notion of self-directed recognitional concepts, articulated by Loar. This approach contrasts with the functional-role approach to mental concepts that is naturally associated with theory theory.

Keywords: concepts, contents, functional role, internal code, introspective code, Loar, mental vehicles,