Abstract
In this paper I deal with Nietzsche's theory of knowledge in the context of 19th century epistemology. In particular, I argue that, even though Nietzsche shows the ontological lack of content of truths (both on the theoretic and on the moral plane), he nevertheless leaves the space for a practical use of them, in a way that can be compared with William James' pragmatism. I thus deal with Nietzsche's and James' concept of "truth", and show their relationship with some outcomes of Ernst Mach's epistemology.