Full Idea
Many concepts have no prototypes; and there are many complex concepts whose prototypes aren't related to the prototypes of their constituents in the way compositional explanation of productivity and systematicity requires.
Gist of Idea
Many concepts lack prototypes, and complex prototypes aren't built from simple ones
Source
Jerry A. Fodor (Concepts:where cogn.science went wrong [1998], Ch.5)
Book Reference
Fodor,Jerry A.: 'Concepts: where cognitive science went wrong' [OUP 1998], p.100
A Reaction
His favourite example of the latter is 'pet fish', where the prototype of 'pet' is hardly ever a fish, and the prototype of 'fish' is usually much bigger than goldfish. Fodor is arguing that concepts are atomic.