Some theories of linguistic meaning, such as those of Paul Grice and David Lewis, make appeal to higher–order thoughts: thoughts about thoughts. Because of this, such theories run the risk of being empirically refuted by the existence of speakers who lack, completely or to a high degree, the capacity of thinking about thoughts. Research on autism during the past 15 years provides strong evidence for the existence of such speakers. Some persons with autism have linguistic abilities that qualify them as (...) speakers, but manifest a severely impaired capacity to understand what it is to have beliefs. (shrink)