In Book 2, Nietzsche developed the idea that underpinning everything all supposedly sacred ideals and values are certain perspectives and interests. He now applies this theory to dominant ideas about consciousness and epistemology. In particular, he criticizes the theory known as positivism, which states that “there are only facts” (267). Nietzsche argues that there are no pure facts “in themselves.” All supposed “facts,” and our broader understanding of the world, are forms of “interpretation.” These interpretations are, in turn, rooted in the struggle for dominance within us of various needs and drives. As Nietzsche says, “it is our needs that interpret the world; our drives and their For and Against” (267). In contrast to “positivism,” Nietzsche proposes “perspectivism.”

Nietzsche likewise questions the idea of the “subject” proposed by the philosopher Descartes, who argued that a human being is a unitary consciousness possessing reason and free will. His main argument is that Descartes’s justification for such a subject draws an undue inference. Descartes says, “there is thinking: therefore there is something that thinks” (268). Nietzsche argues that from the fact that there is thinking it does not follow that there is any “thinking substance,” or subject, of which this thinking is a property.