Tillich's interpretation of the history of philosophy from the renaissance to the present day is an important background-factor. He explains this in an essay, Kairos und Logos: Eine Untersuchung zur Metaphysik der Erkenntnis, written in 1926.¹ In 1927, it reappears in the lecture. Über gläubigen Realismus², and in 1946 in his article The Two Types of Philosophy of Religion.³ His interpretation of this philosophical history runs as an undercurrent throughout most of his writings.