One of the essentials of a good community, that is, a community in which each of us can build flourishing lives for ourselves and those we care about, is tolerance. Tolerance matters for the obvious reason that the diversity of interests and desires people have is sometimes so great that we don't even understand why others should think and behave as they do; and yet we acknowledge their right to do so, because we cherish the same right for ourselves.
Thus, the very possibility of society turns on tolerance. Society involves people getting along peacefully all the time and co-operatively most of the time, and neither is possible unless people recognise the entitlement of others to their choices, and give them space accordingly.
But here, of course, is the familiar rub: the paradox of tolerance, which is that a tolerant society is at risk of tolerating those who are intolerant, and allowing movements to grow which foster intolerance. The profoundly dismaying spectacle of the contemporary Netherlands illustrates this point. What was one of the most inclusive and welcoming societies in Europe has been stabbed in the heart by people it sheltered and who have grown into intolerant activists wishing to impose conformity and censorship on others by violence. And alas, it has happened here [in Scotland], too.
The remedy for the paradox of tolerance is, of course, that tolerance can't tolerate intolerance. But this truism is often greeted with the response that if tolerance is intolerant of something, it is in breach of itself: it becomes self-defeating in another way. The answer is to insist that although it's natural to think that tolerance is a warm, woolly, feel-good attitude, in fact it is a principle: it's an ethical demand that everyone should respect everyone else's rights and liberties. And this does the trick all by itself. Tolerance is not a demand to license just anything whatever, least of all behaviour that threatens the rights of others. Tolerance thus has its central place in the good society along with other principles that stop it from being a merely flabby acceptance that anything goes.
These are the principles of pluralism and individual liberty, which essentially require tolerance, but indicate its rational limit. Insisting on this vital point is what explains why tolerance not only cannot but must not tolerate intolerance.