Abstract
To have a propositional attitude, a thinker must possess the concepts included in its content. Surprisingly, this rather trivial principle refl ects badly on many theories of concept possession because, in its light, they seem to require too much. To solve this problem, I point out an ambiguity in attributions of the form 'S possesses the concept of Fs'. There is an undemanding sense which is involved in the given principle, whereas the theoretical claims concern a stronger sense which can be brought out by formulations such as 'S has an adequate conception of Fs' or 'S knows what Fs are'