[7] Tillich's work attracted scholarship from other influential thinkers like Karl Barth, Reinhold Niebuhr, H. Richard Niebuhr, George Lindbeck, Erich Przywara, James Luther Adams, Avery Cardinal Dulles, Dietrich Bonhoeffer, Sallie McFague, Richard John Neuhaus, David Novak, Thomas Merton, Michael Novak, and Martin Luther King Jr.

According to H. Richard Niebuhr, "[t]he reading of Systematic Theology can be a great voyage of discovery into a rich and deep, and inclusive and yet elaborated, vision and understanding of human life in the presence of the mystery of God.

Tillich was born on August 20, 1886, in the small village of Starzeddel, Province of Brandenburg, then part of Germany (modern-day Starosiedle, Poland).

Then, succeeding Max Scheler (who had died suddenly in 1928), Tillich held the post of "Professor of Philosophy and Sociology"[18] at the University of Frankfurt from 1929 to 1933.

While at Frankfurt Tillich's two assistants (both completing their doctorates under him) were Harald Poelchau and Theodor Adorno (in 1931 Leo Strauss had applied for the same position but was rejected).

[19] During that period Tillich also "was instrumental in hiring Max Horkheimer as the Director of the Institut für Sozialforschung and to a professorship in sociology at the University of Frankfurt.

[22] While at the University of Frankfurt, Tillich traveled throughout Germany giving public lectures and speeches that brought him into conflict with the Nazi movement.

[10] At Union, Tillich earned his reputation, publishing a series of books that outlined his idiosyncratic synthesis of Protestant Christian theology and existential philosophy.

1 brought Tillich international academic acclaim, prompting an invitation to give the prestigious Gifford Lectures in 1953–54 at the University of Aberdeen.

The Courage to Be, which examines ontic, moral, and spiritual anxieties across history and in modernity, was based on Tillich's 1950 Dwight H. Terry Lectureship and reached a wide general readership.

[31] In 1961, Tillich became one of the founding members of the Society for the Arts, Religion and Contemporary Culture, an organization with which he maintained ties for the remainder of his life.

His gravestone inscription reads: "And he shall be like a tree planted by the rivers of water, that bringeth forth his fruit for his season, his leaf also shall not wither.

Traditional medieval philosophical theology in the work of figures such as St. Anselm, Duns Scotus, and William of Ockham tended to understand God as the highest existing being,[44] to which predicates such as omnipotence, omniscience, omnipresence, goodness, righteousness, holiness, etc.

Following his existential analysis, Tillich further argues that theological theism is not only logically problematic, but is unable to speak into the situation of radical doubt and despair about meaning in life.

[58] Traditionally Christian theology has always understood the doctrine of creation to mean precisely this external relationality between God, the Creator, and the creature as separate and not identical realities.

According to Tillich, theological theism has provoked the rebellions found in atheism and Existentialism, although other social factors such as the industrial revolution have also contributed to the "reification" of the human being.

The modern man could no longer tolerate the idea of being an "object" completely subjected to the absolute knowledge of God.

[64]For Tillich, the existential questions of human existence are associated with the field of philosophy and, more specifically, ontology (the study of being).

[66][67] Thus, on one side of the correlation lies an ontological analysis of the human situation, whereas on the other is a presentation of the Christian message as a response to this existential dilemma.

[64] Throughout the Systematic Theology, Tillich is careful to maintain this distinction between form and content without allowing one to be inadvertently conditioned by the other.

Many criticisms of Tillich's methodology revolve around this issue of whether the integrity of the Christian message is really maintained when its form is conditioned by philosophy.

[78]Tillich stated the courage to take meaninglessness into oneself presupposes a relation to the ground of being: absolute faith.

[83]In short, for Tillich, faith does not stand opposed to rational or nonrational elements (reason and emotion respectively), as some philosophers would maintain.

The main supporters of the Fellowship in the early days included Tillich, Eduard Heimann, Sherwood Eddy and Rose Terlin.

[86] Tillich's book The Socialist Decision was published in the early 1930s, during the rise of Nazism, and it was immediately censored by the Nazi regime.

[91] New Age catchphrases describing God spatially as the "Ground of Being" and temporally as the "Eternal Now,"[92] in tandem with the view that God is not an entity among entities but rather is "Being-Itself"—ideas which Eckhart Tolle invoked repeatedly throughout his career[93]—were renovated by Tillich, although these ideas derive from Christian mystics and early theologians such as St. Augustine and St. Thomas Aquinas.

[94][95] A consideration of Tillich's traumatic experiences as an active duty chaplain during World War I has led some to view his theology as "Post-traumatic."

[97] Tillich has been criticized from the Barthian wing of Protestantism for what is alleged to be correlation theory's tendency to reduce God and his relationship to man to anthropocentric terms.

Tillich countered that Barth's approach to theology denies the "possibility of understanding God's relation to man in any other way than heteronomously or extrinsically".

"[101] Defenders of Tillich counter such claims by pointing to clear monotheistic expressions from a classical Christian viewpoint, of the relationship between God and man, such as his description of the experience of grace in his sermon "You Are Accepted".