Noam Chomsky's rationalist account of the human mind has won many adherents and attracted many critics. What has been little noticed on either side of the debate is that Chomsky's rationalism is best viewed as a pair of quite distinct doctrines about the mental mechanisms responsible for language acquisition. One of these doctrines, the one I will call rigid rationalism, entails the other, which I call anti-empiricism, but the entailment is not mutual. Rigid rationalism is much the stronger of the (...) two. What is more, the argument Chomsky offers for rigid rationalism is quite distinct from the argument for anti-empiricism. In the first section of this paper I will set out what I take to be the most favourable interpretation of each of these doctrines, along with the argument supporting it. (shrink)