Tolerance, while proving necessary in today's varied world, can be grudgingly given and resentfully received. Toleration may be necessary, but it has little appeal, and certainly cannot serve as either a central or unifying doctrine in a thriving moral or political philosophy. A deeper understanding of what tolerance requires leads us to see that it demands more. Once we inculcate the attitude of tolerance in ourselves and our politics, tolerance can occupy the difficult and contested. It does not make sense, for instance, if we already fully accept a practice; nor does it make sense if what...