state protects individual rights and makes sure that contracts and other market transactions are voluntary. The meta-utopian framework reveals what is inspiring and noble in this night-watchman function. They both contain the only form of social union that is possible for the atomistic rational agents of Anarchy, State, and Utopia, fully voluntary associations of mutual benefit. The influence of this idea on Nozick's thinking is profound. Even in his last book, Invariances, he is still concerned to give priority to the mutual-benefit aspect of ethics. This coercively enforceable aspect ideally has an empty core in the game theorists' sense: the core of a game is all of those payoff vectors to the group wherein no subgroup can do better for itself acting on its own, without cooperating with others not in the subgroup. The worlds in Nozick's meta-utopia have empty cores. No subgroup of a utopian world is better off to emigrate to its own smaller world. The function of ethics is fundamentally to create and stabilize such empty cores of mutually beneficial cooperation. His view is that we are fortunate to live under conditions that favor "more-extensive cores", and less conquest, slavery, and pillaging, "less imposition of noncore vectors upon subgroups." Higher moral goals are real enough, but they are parasitic (as described in The Examined Life, the chapter "Darkness and Light") upon mutually beneficial cooperation. In Nozick's utopia if people are not happy with the society they are in they can leave and start their own community, but he fails to consider that there might be things that prevent a person from leaving or moving about freely. Thomas Pogge states that items that are not socially induced can restrict people's options. Nozick states that for the healthy to have to support the handicapped imposes on their freedom, but Pogge argues that it introduces an inequality. This inequality restricts movement based on the ground rules Nozick has implemented, which could lead to feudalism and slavery, a society which Nozick himself would reject. David Schaefer notes that Nozick himself claims that a person could sell himself into slavery, which would break the very ground rule that was created, restricting the movement and choices that a person could make. Other topics covered in the book Retributive and deterrence theories of punishment In chapter 4 Nozick discusses two theories of punishment: the deterrence and the retributive ones. To compare them, we have