Heidegger's lecture course at the University of Marburg in the summer of 1925, an early version of Being and Time (1927), offers a unique glimpse into the motivations that prompted the writing of this great philosopher's master work and the presuppositions that gave shape to it. The book embarks upon a provisional description of what Heidegger calls "Dasein," the field in which both being and time become manifest. Heidegger analyzes Dasein...