Liberal political philosophy sometimes seems beset by a curiously naive literal-mindedness. We write as though the tasks of politics were reducible to the choice of principles, and as though principles formulated in the theorist's study could constitute the basic structure of a well-ordered society. We know, of course, that the articulation of principles for a liberal order is a tricky business; they have to be sensitive to all sorts of things, such as the tensions between liberty and equality, equality and opportunity, rights and efficiency, and stability and justice. And so we spend years – collectively we spend decades or generations – debating them, elaborating them, refining them. All this is done in the hope that if only we could get the principles right, we would have a basis for a decent, just, and prosperous social order, which could be enshrined in our laws and constitution.

Occasionally, in the wee small hours of the morning, it occurs to some of us that principles, formulated and refined by theorists, are not necessarily the key to a well-ordered society; laws and constitutions are often eclectic and half-coherent accumulations of wisdom rather than embodiments of well-worked-out principles; and anyway, laws and constitutions are not all that there is to social order. There is also the real world – the world of human nature in its more sordid or less calculable aspects, the world of chance and fortune, of crime, fanaticism, and war, of tears of pride and rage, the real world of faith, patriotism, and other creeds we would like to be able to dismiss as non-rational.