The Phenomenology of Religious Life presents the text of Heidegger's important 1920-21 lectures on religion. The volume consists of the famous lecture course Introduction to the Phenomenology of Religion, a course on Augustine and Neoplatonism, and notes for a course on The Philosophical Foundations of Medieval Mysticism that was never delivered. Heidegger's engagements with Aristotle, St. Paul, Augustine, and Luther give readers a sense of what phenomenology would come to mean in the mature expression of his thought. Heidegger reveals an impressive display of theological knowledge, protecting Christian life experience from Greek philosophy and defending Paul against Nietzsche.