Two countervailing trends mark the intellectual tenor of our age – the spread of naturalistic worldviews and religious orthodoxies. Advances in biogenetics, brain research, and robotics are clearing the way for the penetration of an objective scientific self-understanding of persons into everyday life. For philosophy, this trend is associated with the challenge of scientific naturalism. At the same time, we are witnessing an unexpected revitalization of religious traditions and the politicization of religious communities across the world. From a philosophical perspective, this revival of religious energies poses the challenge of a fundamentalist critique of the principles underlying the modern West's postmetaphysical understanding of itself. The tension between naturalism and religion is the central theme of this major new book by Jürgen Habermas. On the one hand he argues for an appropriate naturalistic understanding of cultural evolution that does justice to the normative character of the human mind. On the other hand, he calls for an appropriate interpretation of the secularizing effects of a process of social and cultural rationalization increasingly denounced by the champions of religious orthodoxies as a historical development peculiar to the West. These reflections on the enduring importance of religion and the limits of secularism under conditions of postmetaphysical reason set the scene for an extended treatment of the political significance of religious tolerance and for a fresh contribution to current debates on cosmopolitanism and a constitution for international society.