Because in politics the most fundamental question is always that of what particular human beings have good reason to do, and because what they do have good reason to do depends directly and profoundly on how far they can and should trust and rely upon one another, I take the central issue in political philosophy (properly so called) to be that of how to conceive the rationality of trust in relation to the causal field of politics.

In this essay I shall be talking about the thinking of Locke, firstly because I consider that he made a more systematic and determined effort to think about this question than any other and more recent political philosopher, and secondly (and, of course, connectedly) because the attempt to think comprehensively about this conception has essentially disappeared from modern political philosophy, both in its Marxist and in its liberal or conservative variants. (There are, to be sure, important analytical idioms in modern thought – such as game theory – and key moments in the construction of particular political theories – such as Rawls' original position – in which the issue is treated with great assurance.) The explanation of this disappearance is a complicated and somewhat obscure matter, and not one suitable for treatment in this context. But that it is so would be difficult to deny.

I discuss Locke, therefore, not because I wish to argue that we should espouse all – or any – of Locke's own detailed conceptions, but because we do, in my view, have good reason to treat his conception of political philosophy as exemplary – as a model which there is still every ground for our trying to emulate.