Paul Tillich (1886-1965) was one of the leading theologians of the twentieth century. Tillich was born in Germany and received his education and first academic appointments there. Tillich left Germany in 1933 to teach at Union Theological Seminary after having been dismissed from his university position by the National Socialist government for his radical views and political associations. In the United States, he became a highly successful lecturer, preacher, and public intellectual who reached numbers of persons who had departed or who had doubts regarding traditional religious belief and practice. Tillich underwent a series of traumatic losses in the early decades of his life that powerfully shaped his subsequent contributions to religious and cultural discourse. This essay outlines this pattern of loss and speculates about its impact upon his theological work. It lifts up Tillich's perspective of living and working "on the boundary" of disciplines, eras, and cultures, most particularly where psychoanalytic ideas contributed to his "theology of culture." It also stresses Tillich's role in initiating the ongoing dialogue between religion and psychiatry and psychoanalysis. The essay concludes with a summary critique of Tillich's work along with an affirmation of his considerable legacy. This essay was originally a presentation for the Richardson Research Seminar in the History of Psychiatry at Weill Cornell Medical College.