The phenomena of human difference and disagreement have set the agenda for this book, and for political philosophy as a whole, from the beginning. As authors from Plato to Rawls illustrate, many political philosophers have sought to overcome the conflicts and disagreements that mark ordinary politics by postulating and delineating comprehensive political ideals (of justice, the common good, human flourishing, the “free society”) by which to judge existing institutions. But while this sort of speculation may be illuminating in many ways, it can also foster an overly simplistic attitude to political disagreement. From the vantage point of such high ideals, the persistence of conflicts between those of fundamentally opposed religious and ethical persuasions may seem trivial and uninteresting, little more than a symptom of the current imperfection of political reality, or of errors destined to pass away once the “truth” is gradually understood and realized.

But surely indulging this thought is both naïvely optimistic and a serious evasion of the complex realities of political conflict. People differ, sometimes very widely, in their beliefs, their modes of conduct, their religious or cultural sensibilities and their identities. We cannot normally expect people to change these often deeply ingrained traits at the drop of a hat, just because we think we have strong philosophical arguments in favor of ways of life, beliefs, and practices they reject. Doing so is often resented and resisted, and a cause of enmity, violence, and war.