Peter Unger

The topic of personal identity has prompted some of the liveliest and most interesting debates in recent philosophy. In a fascinating new contribution to the discussion, Peter Unger presents a psychologically aimed, but physically based, account of our identity over time. While supporting the account, he explains why many influential contemporary philosophers have underrated the importance of physical continuity to our survival, casting a new light on the work of Lewis, Nagel, Nozick, Parfit, Perry, Shoemaker, and others. Deriving from his discussion of our identity itself, Unger produces a novel but commonsensical theory of the relations between identity and some of our deepest concerns. In a conservative but flexible spirit, he explores the implications of his theory for questions of value and of the good life

In this short but meaty book, Peter Unger questions the objective answers that have been given to central problems in philosophy. As Unger hypothesizes, many of these problems are unanswerable, including the problems of knowledge and scepticism, the problems of free will, and problems of causation and explanation. In each case, he argues, we arrive at one answer only relative to an assumption about the meaning of key terms, terms like "know" and like "cause," even while we arrive at an opposite answer relative to quite different assumptions, but equally arbitrary assumptions, about what the key terms mean.

Peter Unger’s book has both substantive and methodological aims. Substantively, it aims to prove the following four claims in the following order: we must, in general, suffer great losses of property to prevent suffering and death; we may, in general, impose such losses on others for the same goals; we may, in general, kill others to prevent more deaths; and we must, in general, kill ourself to prevent more deaths. Methodologically, it aims to show that intuitive judgments about cases that would be presented as evidence against the four substantive claims—the standard technique of nonconsequentialists arguing against consequentialists—are worthless because we can construct cases that generate the opposite intuitive judgment; further, we can show that the factors that distinguish the cases yielding such different intuitions are not morally significant; and hence, we must decide which judgments are correct by consulting such general moral values as the importance of reducing suffering and death. Thus, Unger offers an error theory of nonconsequentialist restrictions on harming others and prerogatives not to make large sacrifices to aid. This error theory is based on the psychological effects of morally insignificant factors.