“To have a right,” wrote John Stuart Mill, is “… to have something which society ought to defend me in the possession of.” The word “possession” makes this statement most easily applicable to the kind of rights that I have called “entitlements,” but we can easily imagine how the thought might be extended to the whole range of rights. All that is required is that we allow the things possessed to include liberties, powers, and immunities, and that for “possession” we read “exercise” or “enjoyment” as appropriate. In the spirit of Mill's dictum, we could then say that to have a right is to have an entitlement, liberty, power, or immunity, the possession, exercise, or enjoyment of which society should defend. But why, exactly, should society defend it? One possibility is that the existence of a right is an independent justification for requiring that defense. Another is that to classify something as a right is to state in a shorthand way that such defense is normatively required but without explaining that requirement's normative underpinnings. Throughout this book, I have argued for the second possibility.

Mill would have agreed. Immediately following the sentence quoted above, he wrote that if asked why society should defend the possession (or enjoyment, or exercise) of things recognized as rights, he would reply that the general utility required it. Mill, of course, was a utilitarian, believing that the general utility was the ultimate justification for all things.