The book describes the fundamental tenets of Catholic Radicalism, defined as an understanding of Christianity from a perspective which dismisses the traditional supernatural image of God. The essentials of Catholic Radicalism are extracted from the works of Vito Mancuso, a lay Italian theologian, whose intention is to rebuild Christian theology starting from the natural and physical reality of this world. Mancuso insists that he is a Catholic theologian despite his conviction that God should be seen today in atheistic terms, which help us understand the world from a rational perspective. The use of reason in theology is compulsory for Mancuso in order for theology to make sense in the skeptical society of our times, which is characterized by a powerful lay consciousness.