 This shift to historical knowledge is the main theme of the notes (ca. 1910) for a second volume of The Formation of the Historical World in the Human Sciences (1910) which were published posthumously in 1927 as Drafts for a Critique of Historical Reason. Here Dilthey analyzes the categories of life that are relevant to historical knowledge. He distinguishes between formal and real categories. Formal categories stem from elementary logical operations that are at work in all apprehension: they include the processes of comparing, noting sameness, differentiating and relating. Although such elementary operations are prediscursive, they provide the basis for discursive thought. The prediscursive noting of sameness prepares the way for the unifying concepts of discursive thought and the process of relating provides the basis for synthetic procedures. These prediscursive and discursive modes of thought account for the formal categories of unity, plurality, identity, difference, degree and relation that are shared by the natural and human sciences.