1886–1900

Adolf von Harnack and liberal theology ("What is Christianity?")

Adolf von Harnack, an ardent follower of Ritschl, taught church history at the University of Berlin from 1888 to 1921. His three-volume History of Dogma (1886–1889) presented the history of Christian thought as a growing "Hellenization."

In the winter of 1899/1900 Harnack gave lectures at the University of Berlin that were taken down in shorthand. They formed the basis of the book The Essence of Christianity ("What Is Christianity?", 1901), in which he called Protestants to return to the original teaching of Jesus. Harnack was the last major representative of 19th-century liberal Protestantism; his former student Karl Barth became his critic.