Ordained a Lutheran clergyman on the conclusion of his university studies, Tillich served as a military chaplain during World War I. The war was a shattering experience to him, not only for its carnage and physical destruction but as evidence of the bankruptcy of 19th-century humanism and the questionableness of the adequacy of autonomy as sole guide. The chaotic situation in Germany after the armistice made him certain that Western civilization was indeed nearing the end of an era.
His practical response to this crisis was to join the Religious-Socialist movement, whose members believed that the impending cultural breakdown was a momentous opportunity for creative social reconstruction, a time that Tillich characterized by the New Testament term kairos, signifying a historical moment into which eternity erupts, transforming the world into a new state of being. But ideas, rather than political activity, were his main interest. At teaching posts in the universities of Berlin, Marburg, Dresden, Leipzig, and Frankfurt he participated eagerly in discussion groups searching for a new understanding of the human situation. He also wrote extensively, publishing more than 100 essays, articles, and reviews in the period 1919–33.
In most of these writings Tillich was using the insight he had gained at Halle as a norm in analyses of religion and culture, the meaning of history, and contemporary social problems. The remarkable work, Das System der Wissenschaften nach Gegenständen und Methoden (“The System of the Sciences According to Their Subjects and Methods,” 1923), was his first attempt to render a systematic account of man's spiritual endeavours from this point of view. As early as 1925, in Marburg, he was also at work on what was to become his major opus, Systematic Theology, vol. 3: Life and the Spirit: History and the Kingdom of God (1951–63). --Copyright © Encyclopædia Britannica
