Philosophers have usually argued that the right way to explain people's actions is in terms of their beliefs and intentions rather than in terms of objective facts. Rowland Stout takes the opposite line in his account of action. Appeal to teleology is widely regarded with suspicion, but Dr Stout argues that there are things in nature, namely actions, that can be teleologically explained: they happen because they serve some end. Moreover, this teleological explanation is externalist: it cites facts about the world, not beliefs and intentions which only represent the world. Such externalism about the explanation of action is a natural partner to externalism about knowledge and about reference, but has hardly ever been considered seriously before. One dramatic consequence of such a position is that it opens up the possibility of a behaviourist account of beliefs and intentions.