Source : Webster's Revised Unabridged Dictionary (1913)

Conceptualism \Con*cep"tu*al*ism\, n. (Metaph.)
   A theory, intermediate between realism and nominalism, that
   the mind has the power of forming for itself general
   conceptions of individual or single objects. --Stewart.

Source : WordNet®

conceptualism
     n : the doctrine that the application of a general term to
         various objects indicates the existence of a mental
         entity that mediates the application