useful translation from logic and set-theory back to scientific knowledge. If no translation between scientific knowledge and the logical structures can be constructed that works both ways, then the properties of the purely logical and set-theoretic constructions do not usefully inform understanding of scientific knowledge. On Quine's account, attempts to pursue the traditional project of finding the meanings and truths of science philosophically have failed on their own terms and failed to offer any advantage over the more direct methods of psychology. Quine rejects the analytic-synthetic distinction and emphasizes the holistic nature of our beliefs. Since traditional philosophic analysis of knowledge fails, those wishing to study knowledge ought to employ natural scientific methods. Scientific study of knowledge differs from philosophic study by focusing on how humans acquire knowledge rather than speculative analysis of knowledge. According to Quine, this appeal to science to ground the project of studying knowledge, which itself underlies science, should not be dismissed for its circularity since it is the best option available after ruling out traditional philosophic methods for their more serious flaws. This identification and tolerance of circularity is reflected elsewhere in Quine's works. Cooperative naturalism Cooperative naturalism is a version of naturalized epistemology which states that while there are evaluative questions to pursue, the empirical results from psychology concerning how individuals actually think and reason are essential and useful for making progress in these evaluative questions. This form of naturalism says that our psychological and biological limitations and abilities are relevant to the study of human knowledge. Empirical work is relevant to epistemology but only if epistemology is itself as broad as the study of human knowledge. Substantive naturalism Substantive naturalism is a form of naturalized epistemology that emphasizes how all epistemic facts are natural facts. Natural facts can be based on two main ideas. The first is that all natural facts include all facts that science would verify. The second is to provide a list of examples that consists of natural items. This will help in deducing what else can be included. Criticism Quine articulates the problem of circularity inherent in naturalized epistemology when it is treated as a replacement for traditional epistemology. If the goal of traditional epistemology is to validate or to provide the foundation for the natural sciences, naturalized epistemology would be tasked with validating the natural sciences by means of those very sciences. That is, an empirical investigation into