The Fodorian central objections to Inferential Role Semantics can be taken to include an ‘Analyticity Challenge’ and a ‘Circularity Challenge’, which are ultimately challenges to IRS explanations of concept possession. In this paper I present inferential role theories, critically examine these challenges and point out two misunderstandings to which they are exposed. I then state in detail a rationalist version of IRS and argue that this version meets head on the Fodorian challenges. If sound, these considerations show that there is (...) no problem of principle in the consideration of IRS as a good candidate for a theory of concepts. (shrink)