"Anxiety" is one of the best starting points to comprehend Tillich's Existential Psychology. Tillich's life history and some remarkable incidents in his life greatly influenced his doctrine of man; tragic events caused deep anxiety and strong impact on his thought. Apart from anxiety, the idea of demonic, which later became the main subject of the renowned existential psychologist Rollo May (1909-1994), also played a crucial role in the formation of Tillich's theology.
The important role of anxiety and demonic in the field of existential psychology and therapy affected the ontological perspective of Tillich, who embraced the idea of "non-being" in a positive way. Tillich's theology can be seen as a journey of self-exploration and psychological process of redemption by means of academic forms. This explains why his theological issues and methodology were not the same as his contemporaries and they have become important elements in the field of existential psychology.