Martin Heidegger (1889–1976) was born in Messkirch, a small town in the hills of southwestern Germany. The environment of his modest, middle class upbringing was that of a Catholic agrarian village where his father was the sexton of the local church. When Heidegger was fourteen he entered the Catholic seminary at Constance and began an education that appeared to be directed toward a vocation in the priesthood. He entered a novitiate with the Jesuits in 1909 but left that track after a short time and shifted out of clerical training altogether in 1911. He intensified his studies in philosophy, literature, and science, and for a time concentrated on mathematics. During this period (through 1915) he developed a conservative approach to neo-scholastic thought and published articles in conservative Catholic journals. He also read intensely the emerging phenomenological literature and neo-Kantian philosophy.

Heidegger's doctoral dissertation in 1913 had the title, "The...