The aim of this paper is to discuss some constitutive traits of contemporary naturalism, by focusing in particular on its two main varieties: scientific naturalism and liberal naturalism. Although they share some general assumptions, these two forms of naturalism also differ in several respects. My argument is primarily focused on the critical discussion of the three main theses of scientific naturalism: (1) the constitutive thesis, (2) the anti-foundational thesis, and (3) the continuity thesis. In the last section, I will show in what sense liberal naturalism is different from scientific naturalism with respect to these three claims, and in particular with respect to the continuity thesis.