In section 1 I offer a definition of “psychologism” which applies to many of the apparently quite disparate uses that philosophers have made of the term. In section 2 I map out some distinct varieties of psychologism. In a short section 3 I indicate how the changing academic climate has injected a new urgency into the debate on psychologism. In section 4 I offer an argument for a variety of psychologism which has important consequences for cognitive science, and in section 5 I consider some objections to the argument.