Naturalism as a philosophy of nature, what it consists in, and our ways of knowing nature (so conceived) has a long history in philosophy. In the twentieth century the question of naturalism has been, for the most part, centrally concerned with the question of philosophy’s relation to science, especially the natural (or “hard”) sciences. Its moral is that philosophy can no longer continue to think of itself as an autonomous discipline or stance distinct from science. I will proceed by examining in some detail the naturalisms of W. V. O. Quine and David Armstrong, which seem to align as a result of a commitment to what, at first, seem the same doctrines of Physicalism, Empiricism, and Metaphysical Realism. Against this perception of near-alignment I want to argue that they do not neatly line up on the naturalist side of the longstanding opposition between idealism and naturalism. In fact, in some key respects, Quine’s naturalism contains traces of idealism. The real opposition is between normativism and naturalism. I conclude by briefly contrasting two normativist positions – idealism and liberal naturalism – and come down in favor of the latter.