Religions pose special challenges to liberal ways of justifying political authority. For while liberals generally wish to allow the utmost freedom to religions, they often also wish to justify political authority by the (at least hypothetical) consent of those subject to it, and thus to uphold certain more distinctive ideas of freedom and equality. But religions need neither share this peculiar liberal concern nor provide justifications that agree with liberal ones—they may prioritize doctrine over reason or illiberal hierarchies over equality, say. Indeed, the wealth of different religious sensibilities, voices, and demands present in contemporary liberal societies makes these challenges particularly urgent. In the United States, for instance, while strong Christian forces have persisted, neo-Protestant movements and an unprecedented array of other new religious groups and sensibilities have also emerged. In Europe, while the traditional Christian churches have declined, they have been replaced not only by more “secular” cultures, but also by new forms of Christian and other religious influences, including the oft-emphasized Islamic ones.1 While liberals may wish to embrace these religious phenomena, they are often also wary of their potential for destabilizing liberal structures of political authority, whether by disturbing these structures directly or by upsetting consensus over them. This book explores these challenges by reexamining perhaps the most sophisticated, influential, and controversial liberal response to them, that of John Rawls.