The key problem of philosophy of language is that "how the language-understanding is possible?",and it is the aim that Davidson’s Program deals with.In this essay,we try to elaborate that the semantic externalism,which proposed by Davidson based his critical investigation on social externalism and perceptual externalism,is a necessary condition to make the language-understanding possible.This idea can be demonstrated in two aspects:first,it provides a semantic-ontological basis for objective truth of belief in the communication;second,it makes the skeptic assumption impossible that our belief would be systematic error,thus it offers a new approach to refute skepticism.
