He considers three leading theories about what we ought to do — one

36 He considers three leading theories about what we ought to do — one deriving from Kant, one from the social-contract tradition of Hobbes, Locke, Rousseau, and the contemporary philosophers John Rawls and T.M. Scanlon, and one from Bentham’s utilitarianism — and argues that the Kantian and social-contract theories must be revised in order to be defensible. Then he argues that these revised theories coincide with a particular form of consequentialism, which is a theory in the same broad family as utilitarianism. If Parfit is right, there is much less disagreement between apparently conflicting moral theories than we all thought. The defenders of each of these theories are, in Parfit’s vivid phrase, “climbing the same mountain on different sides.” Readers who go to On What Matters seeking an answer to the question posed by its title might be disappointed. Parfit’s real interest is in combating subjectivism and nihilism. Unless he can show that objectivism is true, he believes, nothing matters. When Parfit does come to the question of “what matters,” his answer might seem surprisingly obvious. He tells us, for example, that what matters most now is that “we rich people give up some of our luxuries, ceasing to overheat the Earth’s atmosphere, and taking care of this planet in other ways, so that it continues to support intelligent life.” Many of us had already reached that conclusion. What we gain from Parfit’s work is the possibility of defending these and other moral claims as objective truths. Peter Singer is Professor of Bioethics at Princeton University and Laureate Professor at the University of Melbourne. Revised editions of his books Practical Ethics and The Expanding Circle have just been published. HOUSE_OVERSIGHT_031911