  Many philosophers deny that there are propositions precisely because they accept the validity of these Easy Arguments (and the truth of certain attitude ascriptions). There are familiar problems besetting the believer in abstract entities. The two “Benacerraf problems,” in particular have received much attention in the literature: the epistemological problem and identification problem. The epistemological problem for abstract propositions, roughly, is this: how can we know about abstract propositions, given that we cannot causally interact with them? The identification problem requires a bit more explanation. If propositions are abstract, then there will be many distinct candidates for propositions which seem to play the proposition role equally well. If certain entities, the Fs, are candidates for being propositions, why won’t the entities consisting of an F paired with the number 1 count as adequate candidates as well, so long as we reconstrue predicates for propositions in such a way as to make the number 1 irrelevant? But propositions cannot be both Fs and these new entities, because these new entities are not Fs. Is it simply indeterminate what propositions are? See the entry on  platonism: in metaphysics.  (See also J. Moore 1999)