How is theology related to philosophy? Can theologians ignore philosophy, or is it bound up with the entire theological project, to be ignored only at the price of incoherence? German Idealism is the sun which illumines all of modern theology. Ignored, distortion and darkness in the interpretation of modern theology become inevitable. Paul Tillich was one of the greatest twentieth century theologians, and his attempt to explain the Fall of humanity and the cosmos illustrates his profound, yet not fully acknowledged, debt to Kant and German Idealism.