Propositions and Attitude Ascriptions: A Fregean Account

When I say ‘Hesperus is Phosphorus’, I seem to express a proposition. And when I say ‘Joan believes that Hesperus is Phosphorus’, I seem to ascribe to Joan an attitude to the same proposition. But what are propositions? And what is involved in ascribing propositional attitudes? Frege held distinctive views on both of these questions. He held that when one says ‘Hesperus is Phosphorus’, one expresses a thought, which is itself determined by composing of the senses of the sentence’s parts. Senses are fine-grained entities, tied to modes of presentation of an object. The senses of ‘Hesperus’ and ‘Phosphorus’ are distinct, as they involve distinct modes of presentation of the same object. Correspondingly, the thought expressed by ‘Hesperus is Hesperus’ is differs from that expressed by ‘Hesperus is Phosphorus’. Frege also held that when one says ‘John believes that Hesperus is Phosphorus’, one ascribes a relation between John and the thought expressed by ‘Hesperus is Phosphorus’. He held that in indirect contexts, such as those inside the scope of ‘believes’, expressions refer to their customary senses. So in the sentence above, ‘Hesperus’ refers to its customary sense rather than to Venus. More crucially, ‘that Hesperus is Phosphorus’ here refers to the thought that ‘Hesperus is Phosphorus’ usually expresses, and the ascription will be true if John stands in a belief relation to that thought. Frege’s views on these questions are no longer as popular as they once were. But I am inclined to think that they are correct, at least in broad outline if not in every detail. In particular, I think it is plausible that sentences express entities that