In the previous chapter, we saw that it was a strengthened will to truth that allowed Nietzsche to see his way past the falsification thesis and to adopt sensualism, the view that the senses are causal conditions for knowledge, as a “regulative hypothesis.” This sensualism arises not from foundationalist philosophizing about the nature of knowledge, but out of recognition of the success of the natural sciences (physiology, in BGE 15) in getting the truth about the world. Nietzsche’s is therefore a naturalized epistemology, an empirical and therefore descriptive hypothesis. That said, we saw that Nietzsche takes the success of empirical inquiry to imply a heuristic principle that has regulatory importance for our behavior: it tells us how to proceed in attempting to acquire knowledge without having to claim that a priori knowledge is logically impossible. The point is that, given our best theory of how we in fact acquire the knowledge we take ourselves to have, we should turn our backs on the quest for a priori knowledge and devote ourselves to empirical explanations.

But this evidently amounts to naturalism. On Brian Leiter’s recent account of it, Nietzsche’s naturalism is methodological naturalism, the doctrine that philosophy should follow the methods of the sciences, the empirical sciences. Why should philosophy follow these methods? Leiter’s answer is basically that these methods have “delivered the goods,” that is, allowed us to find whatever truth we have been able to find beyond that accessible to ordinary perception and common sense. If this is all there is to naturalism, it is equivalent to the claim that philosophy should accept empiricism, “at least as a regulative hypothesis.” In that case, we should take BGE to commit Nietzsche to naturalism. Indeed, the book contains what is probably the most striking and frequently quoted expression of Nietzsche’s commitment to naturalism, his description of his “task” as that of “translat[ing] human beings back into nature,” of “becom[ing] master over the many vain and overly enthusiastic interpretations and connotations that have so far been scrawled and painted over that eternal basic text of homo natura” (BGE 230)