 Stalnaker attempts to escape this difficulty by characterizing mathematical belief as belief about sentences: The belief that the sentence “1 + 1 = 2” expresses a truth and the belief that the sentence “the cosine of 0 is 1” expresses a truth have different content and may differ in truth value between possible worlds (due simply to possible variations in the meanings of terms, if nothing else). However, it’s probably fair to say that few philosophers follow Stalnaker in this view (see discussion in Robbins 2004; and Rayo 2013 for a recent view similar to Stalnaker’s). The apparent difficulty of sustaining such a view of belief is often held to reflect badly on the a coarse-grained possible-worlds view of propositions in general, since it’s generally thought that one of the principal metaphysical functions of propositions is to serve as the contents of belief and other “propositional attitudes” (e.g., Field 1978; Soames 1987).