Tillich was a professor of theology and philosophy at a number of German universities before he was expelled by the Nazi regime for his ties with the Religious Socialists and his vehement anti-Nazi stand. He emigrated to the United States in 1933 and taught at Union Theological Seminary in New York (1933-1955), Harvard University (1955-1962), and the University of Chicago (1962-1965).
Tillich’s major teaching in Dynamics of Faith (1957), the classic introduction to his thought, is the significance of faith as ultimate concern, which means that the unpredictable, and often forceful, penetration of the abstract (“ultimate”) into one’s consciousness elicits a concrete response (“concern”), making the revelationary manageable in one’s own Weltanschauung (worldview). The experience of ultimate concern is a continual process of unconditional correlation of opposite but related elements (subject/object, particular/ universal; law/freedom, and so forth), which Tillich views as the essential-existential ground of being, intellectually and emotionally. A true ultimacy, such as God-centrism, is worthy of human commitment, and such an ultimacy is reached by means of an assemblage of rites and symbols that point to and participate in but never replace the sacredness of an ultimate concern. A false ultimacy is an ultimate commitment to that which is not ultimate (idolatry) and opens the way to the demonic. Thus, for Tillich, the absolutization of Jesus, in opposition to orthodox Christology, is a form of heresy (Christolatry).
Though Tillich’s categories of thought are not easily classified, this quintessential liberal Protestant thinker always wrote in the spirit of Ecclesia Semper Reformanda, as his complete works and supplementary volumes (Stuttgart, 1959-1981) show clearly. In his last public address (at the Divinity School of the University of Chicago, on October 12, 1965), “The Significance of the History of Religions for the Systematic Theologian” (The Future of Religions, 1966), he expressed limitations both in the supersessionist view of traditional Christian theology and the contemporary views of neo-orthodoxy and the “God is dead” movement, and he proposed that future Christian systematic theology needs to consider the basic insights of other world religions. He taught as he lived—“on the boundary.”