 The possibility of reasonable pluralism softens but does not solve the challenge of legitimacy: how one law can legitimately be imposed on diverse citizens. For even in a society of reasonable pluralism, it would be unreasonable to expect everyone to endorse, say, a reasonable Catholicism as the basis for a constitutional settlement. Reasonable Muslims or atheists cannot be expected to endorse Catholicism as setting the basic terms for social life. Nor, of course, can Catholics be expected to accept Islam or atheism as the fundamental basis of law. No comprehensive doctrine can be accepted by all reasonable citizens, and so no comprehensive doctrine can serve as the basis for the legitimate use of coercive political power.