 Russellians have offered a variety of responses to Frege’s puzzle. Many Russellians think that our intuition that sentences like  (19)  and  (20)  can differ in truth-value is based on a mistake. This mistake might be explained at least partly in terms of a confusion between the proposition semantically expressed by a sentence in a context and the propositions speakers would typically use that sentence to pragmatically convey (Salmon 1986; Soames 2002), or in terms of the fact that a single proposition may be believed under several “propositional guises” (again, see Salmon 1986), or in terms of a failure to integrate pieces of information stored using distinct mental representations (Braun &amp; Saul  2002).[3]  Alternatively, a Russellian might try to make room for (19) and (20) to genuinely differ in truth-value by giving up the idea that sentences which differ only in the substitution of proper names with the same content must express the same proposition (Taschek 1995, Fine 2007).