Short answers, pulled from the story.
Paul Tillich (1886-1965) was a German-American Christian existentialist philosopher and Lutheran theologian widely regarded as one of the most influential theologians of the twentieth century. He taught at Union Theological Seminary, Harvard University, and the University of Chicago, and his work attracted engagement from thinkers including Karl Barth, Reinhold Niebuhr, Dietrich Bonhoeffer, and Martin Luther King Jr.
Tillich argued that God is not a being among other beings, even the highest being, but rather being-itself, the ground and power of being that precedes and underlies all existence. He called the conventional view of God as a supreme entity theological theism and considered it bad theology, because it makes God a part of reality and therefore finite in some sense.
In The Courage to Be (1952), Tillich identifies anxiety about fate and death, anxiety about guilt and condemnation, and anxiety about meaninglessness and emptiness. He linked these to different historical eras and argued that the anxiety of meaninglessness was the defining spiritual challenge of the twentieth century.
On the 13th of April 1933, ten weeks after Adolf Hitler became German Chancellor, Tillich was summarily dismissed from his tenured position at the University of Frankfurt along with Karl Mannheim and Max Horkheimer. They were described as among the first batch of prominent academic enemies of the Reich removed for ideological and racial reasons.
The method of correlation is Tillich's approach of pairing the existential questions raised by philosophy and human experience with the answers provided by Christian revelation. Philosophy and ontology develop the questions; theology develops the answers. The form of the theological answer is shaped by the character of the question, while the content comes from the revelatory sources of scripture, church history, and the history of religion and culture.
Tillich's ashes were interred in 1966 in the Paul Tillich Park in New Harmony, Indiana. His gravestone bears a verse from Psalm 1:3: and he shall be like a tree planted by the rivers of water, that bringeth forth his fruit in his season, his leaf also shall not wither.