The influence of Christianity on the intellectual development of Heidegger can hardly be exaggerated. Heidegger was born in a conservative Catholic family. He first entered university as a student of theology. Even after his formal break with the system of Catholicism, he still considered himself a Christian theologian, and as late as 1935, he still had to struggle with the faith of his birth. The theme of this treatise is the Christian influence on Heidegger as it is displayed in Being and Time. It aims at showing that many important concepts in this opus magnum of Heidegger have their origin in Christian thought.