The paper focuses on James’s naturalism as a paradigmatic indicator of the common project of the pragmatist movement that, in contrast with prevailing interpretations, is presented as consisting of differentiated yet complementary ways to perform philosophical activity. The author reconstructs James’s main epistemological, ethical and metaphysical arguments aiming at showing how his philosophy is embedded to Darwin’s biology in such a way that represents the theoretical signposts of pragmatism, especially the shared attentiveness to continuism and fallibilism. The article particularly underlines James’s disapproval of both ontological and methodological reductionisms as well as his denunciation of the various forms of dogmatism generated from philosophical or scientific craving for "absolutes". Such an attitude merges James’s contingentism that is in fact coherent with his criticism of the interpretation of the Darwinian principle of "natural selection" in an absolutist key as well as with his appreciation of Darwin’s suggestion of ambiguity as the most authentic cipher of physical and human reality.
Keywords: William James, continuism, non-reductive naturalism, radical humanism, radical empirism.