Empiricism, the philosophical theory that all our ideas and knowledge are derived from experience, has in recent years been the target of radical and persuasive objections. In the seventeenth century, and for long after, rationalism seemed the only alternative to empiricism, but, like Kant, many contemporary philosophers have been convinced that empiricism and rationalism are equally unacceptable, and that both positions, and the conflict between them, are the result of trying to answer confused, misleading, and perhaps senseless questions. Of all the traditional theories in particular, none, I suppose, has looked to modern philosophers less capable of being revived than the rationalist doctrine of innate ideas: the doctrine that some at least of our ideas and knowledge of things are not derived from outside the mind, through experience, but are present from birth in the mind itself and thus represent the mind's own contribution to our understanding of reality. What Strawson has called ‘those old and picturesque debates regarding the origin of our ideas’ seemed to have become museum pieces, charming, as antiques can be, but with little relevance to current issues. These complacent attitudes, if that is what they are, have been rudely disturbed by Chomsky and his colleagues. Chomsky has suggested ‘that contemporary research supports a theory of psychological a priori principles that bears a striking resemblance to the classical doctrine of innate ideas’. In the prevailing situation, the novelty of this suggestion is twofold. It is not only that the theory of innate ideas may be true after all, but also that the support alleged for the ancient doctrine has a distinctively modern look. The research that Chomsky claims supports the doctrine is research in the empirical science of linguistics. The implication is that empiricism is refutable empirically, and more generally that a philosophical dispute such as the dispute between empiricism and rationalism, once it is made clear, can be settled by science.