 Differences in the content of mental states are also commonly thought to be revealed by certain logical features of sentences we use to report them. Reports of thoughts or beliefs and other intentional states (like intention, hope, fear) often do not seem to retain their truth value when co-extensive expressions are substituted in “that-clauses”. For example: “Barack Obama” and “the 44th president of the United States” are co-extensive or co-referential. And if it’s true that Barack Obama was born in Hawai‘i, it’s true that the 44th U.S President was. Even so, Sam can think that Barack Obama was born in Hawai‘i without thinking that the 44th U.S President was. It seems plausible that this “failure of substitutivity” reflects the fact that just what Sam might be said to think—the “contents” of his thoughts—differ in such a case. Or, as it is sometimes said, intentional states relate to the conditions that would satisfy them, or to what they are about, only “under some aspects” and not others—and differences in the “aspect under which” are differences in content. (Searle speaks here of the “aspectual shape” of intentional states.)