We join this first fundamental question with a second, that of toleration understood in a general way. The political culture of a democratic society is always marked by a diversity of opposing and irreconcilable religious, philosophical, and moraldoctrines. Some of these are perfectly reasonable, and this diversity among reasonable doctrines political liberalism sees as the inevitable long-run result of the powers of human reason at work within the background of enduring free institutions. Thus, the second question is what are the grounds of toleration so understood and given the fact of reasonable pluralism as the inevitable outcome of free institutions? Combining both questions we have: how is it possible for there to exist over time a just and stable society of free and equal citizens, who remain profoundly divided by reasonable religious, philosophical, and moral doctrines?
The most intractable struggles, political liberalism assumes, are confessedly for the sake of highest things: for religion, for philosophical views of the world, and for different moral conceptions of the good. We should find it remarkable that, so deeply opposed in these ways, just cooperation among free and equal citizens is possible at all. In fact, historical experience suggests that it rarely is. If the problem addressed is all too familiar, political liberalism proposes, I believe, a somewhat unfamiliar resolution of it. To state this resolution we need a certain family of ideas. In this lecture I set out the more central of these and offer a definition at the end (§8).
