 Perhaps the most widely known objection to compositionality comes from the observation that even if e and \(e'\) are synonyms, the truth-values of sentences where they occur embedded within the clausal complement of a mental attitude verb may well differ. So, despite the fact that ‘eye-doctor’ and ‘ophthalmologist’ are synonyms (7) may be true and (8) false if Carla is ignorant of this fact: