What do we humans claim when we define ourselves as thinking beings? What do we mean when we claim to know something? What can we know at all? How autonomous is our thinking? When can we claim something to be true? How certain and truthful are the insights provided by the natural sciences? To what are we committed for all our knowing? Such and other questions are being addressed from the perspective and the tradition of existential thought. The trilogy What Obligates Us raises the question about the ethical foundation of the human condition. This second part has human thinking as its specific scope. Like no others, existential philosophers have questioned the power and impotence of science, as they have addressed the many beliefs and certainties that humans appropriated for themselves. Central insights from the works of Kierkegaard, Heidegger, Wittgenstein and Gadamer inspire the book's quest for the particular nature of being human and our claims to be able to know anything at all. Beyond its specific questions, the work also lends itself to being read as an introduction into existential philosophy or into philosophy as such.