Paul Tillich's The Courage to Be is a philosophical work that explores the concept of courage in the face of life's ultimate questions. It examines the idea of faith and its relationship to courage, and how courage can be used to confront the anxiety of life's uncertainties
From Wikipedia
Paul Johannes Tillich was a German and American Christian existentialist philosopher, religious socialist, and Lutheran theologian who was one of the most influential theologians of the twentieth century. Tillich taught at German universities before migrating to the United States in 1933, where he taught at Union Theological Seminary, Harvard University, and the University of Chicago.