 The possible worlds approach to belief content is sometimes referred to as a “coarse-grained” approach because it implies that any two beliefs that would be true in exactly the same set of possible worlds have the same content—as opposed to a “fine-grained” approach on which beliefs that would be true at exactly the same set of possible worlds may nonetheless differ in content. The difference between these two approaches is brought out most starkly by considering mathematical propositions. On standard accounts of possibility, all mathematically true propositions are true in exactly the same set of possible worlds—every world. It seems to follow, on the coarse-grained view, that the belief that 1 + 1 = 2 has exactly the same content as the belief that the cosine of 0 is 1, and thus that anyone who believes (or fails to believe) the one accordingly believes (or fails to believe) the other. And that seems absurd.