If two subsentential expressions had the same content but differed in reference, there could exist two sentences with the same content that differ in truth-value.

If this holds for sentences, does it also hold for subsentential expressions? It seems that it must. Suppose for reductio that two subsentential expressions, e and e*, have the same content but differ in reference. It seems plausible that two sentences which differ only by the substitution of expressions with the same content must have the same content. (While plausible, this principle is not uncontroversial; see entry on compositionality.) But if this is true, then sentences which differ only