:Many writers have expressed scepticism about the explanatory power of transformational generative grammar, but little of this scepticism has been aimed towards formal semantics for natural languages. To a large extent, this neglect is a consequence, not of widespread agreement, but of a lack of clarity, about the aims of philosophers and linguists who construct these semantic theories. Here I hope to make clear a sense in which these theories are explanatory. In short, I argue that the importance and legitimacy (...) of semantics rests on its contribution to epistemology. First, I argue that what distinguishes someone who understands a language from someone who does not is not any linguistic or non‐linguistic behavior but rather the capacity to acquire certain justified beliefs upon hearing another's utterances. It is this justificatory element which is the chief mark of understanding. Second, I argue that in order for someone to have this capacity to acquire certain justified beliefs he must have knowledge of the meanings of the sentences in question. (shrink)