This book began as an attempt to solve some of the problems which twentieth-century philosophers have found in writing about rights. The thirty years since the war have witnessed a curious phenomenon: the language of human rights plays an increasingly important part in normal political debate, while academic political philosophers find it on the whole an elusive and unnecessary mode of discourse. With the exception of Robert Nozick, no major theorist in the Anglo-Saxon world for almost a century has based his work on the concept of a right, and when most philosophers have looked closely at the concept it has seemed to collapse quickly into other, less intractable notions. One argument in particular has meant that the language of rights is difficult to use straightforwardly: it is the famous argument stemming ultimately (as we shall see) from Samuel Pufendorf, though generally associated with Bentham, that to have a right is merely to be the beneficiary of someone else's duty, and that all propositions involving rights are straightforwardly translatable into propositions solely involving duties. If this is true, then the language of rights is irrelevant, and to talk of ‘human rights’ is simply to raise the question of what kinds of duty we are under to other human beings, rather than to provide us with any independent moral insights. The residual Utilitarianism of many Anglo-American political theorists has made this argument particularly attractive, but its force has always largely been that it appears to embody a logical truth.