Abstract：Fodor regards the complexity and formation of thoughts, the systematization of language understanding and proofs of introspection as the basic reasons of the existence of mental language. And he expounds hypothetical mental language from the perceptive of innate language, non-verbal organism, thought's non-vagueness and non-expression, belief division, and so on. This paper doubts the difficult theoretical questions facing these thoughts and points out that Foder's thought is unconvincing, people must think with mental language not natural or oral language.
