Full Idea
Commonsense belief/desire psychology explains vastly more of the facts about behaviour than any of the alternative theories available. It could hardly fail to; there are no alternative theories available.
Gist of Idea
Folk psychology is the only explanation of behaviour we have
Source
Jerry A. Fodor (Psychosemantics [1987], p.x)
Book Reference
Fodor,Jerry A.: 'Psychosemantics' [MIT 1993], p.-7
A Reaction
The alternative view wouldn't expect a clear-cut theory, because it deals with the endless complexity of brain events. The charge is that Fodor and co oversimplify their account, in their desperation for a 'theory'.