 The methodology of epistemology in the period reflects a similar tension. Given the epistemological role of Descartes’ famous “cogito, ergo sum” in his system of knowledge, one might see Descartes’ epistemology as already marking the transition from an epistemology privileging knowledge of God to one that privileges self-knowledge instead. However, in Descartes’ epistemology, it remains true that knowledge of God serves as the necessary foundation for all human knowledge. Hume’s Treatise displays such a re-orientation less ambiguously. As noted, Hume means his work to comprise a science of the mind or of man. In the Introduction, Hume describes the science of man as effectively a foundation for all the sciences since all sciences “lie under the cognizance of men, and are judged of by their powers and faculties.” In other words, since all science is human knowledge, scientific knowledge of humanity is the foundation of the sciences. Hume’s placing the science of man at the foundation of all the sciences both exemplifies the privilege afforded to “mankind’s study of man” within the Enlightenment and provides an interpretation of it. But Hume’s methodological privileging of humanity in the system of sciences contrasts sharply with what he says in the body of his science about humanity. In Hume’s science of man, reason as a faculty of knowledge is skeptically attacked and marginalized; reason is attributed to other animals as well; belief is shown to be grounded in custom and habit; and free will is denied. So, even as knowledge of humanity supplants knowledge of God as the keystone of the system of knowledge, the scientific perspective on humanity starkly challenges humankind’s self-conception as occupying a privileged position in the order of nature.