Parfit, Derek (1942–)

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Derek Parfit is senior research fellow of All Souls College; a regular visiting professor at Harvard, New York University, and Rutgers; and a fellow of both the British Academy and the American Academy of Arts and Sciences.

Born in China and educated in England at the Dragon School and Eton, Parfit took his degree in modern history at Oxford University and later turned to philosophy. He is legendary as a mentor and for his acute monograph-length criticisms of manuscripts, as well as for his important contributions to ethics, practical reasoning, and metaphysics. Parfit is widely regarded as one of the most important contemporary philosophers.

Along with John Rawls's A Theory of Justice, Parfit's magnum opus, Reasons and Persons, helped turn ethics from a moribund and peripheral subject that largely focused on the meanings of moral terms into a vibrant and central philosophical topic. Brimming with ingenious examples, powerful arguments, and startling conclusions, it has significantly shaped the philosophical agenda, introducing into discussion a host of new topics, examples, and terminology.

In Part One, Parfit discusses the ways in which theories about morality and rationality can be self-defeating and also makes claims about rational irrationality, blameless wrongdoing, imperceptible harms and benefits, harmless torturers, and other mistakes in moral mathematics. Part Two defends a theory of individual rationality, the Critical Present-aim Theory, which rejects both purely desire-based instrumental theories and a purely self-interested or egoistic theory. Parfit offers a new outlook on the old question of whether morality must lose out in a conflict with prudence or rational egoism. Parfit notes that rational egoism is a hybrid position, neutral with respect to time but partial with respect to persons. Correspondingly, it can be challenged from one direction by morality, which is neutral with respect to both persons and time, and from the other direction by a present-aim theory, which is partial with respect to both persons and time. Parfit suggests that rational egoism rests on an unstable middle ground that requires a firm distinction between persons and time that is metaphysically dubious. Of additional interest are Parfit's insights regarding the rationality of attitudes to time and time's passage.

In Part Three, Parfit propounds a reductionist account of personal identity, somewhat like the Buddhist no-self view. Appealing to a dazzling array of so-called puzzle cases involving hypothetical fission, fusion, and branch lines of different selves or person-stages, Parfit challenges widely held beliefs about the nature and importance of personal identity. Most assume that there is a deep, further fact that constitutes personal identity, a fact that must be all or nothing and that matters greatly in rational and moral deliberations. On Parfit's view, while the logic of identity is all or nothing, the relations that constitute personal identity over time are matters of degree, and sometimes there may be no answer to the question of whether a future self will be me. What matters in survival are physical and psychological continuities with the right kind of cause, where the right kind of cause, he provocatively suggests, might be any cause.

Part Four presents a host of puzzles and paradoxes regarding future generations. The Non-Identity Problem is raised by the fact that any choice between two social or economic policies will affect who it is who will later live. Even if one's choice between two such policies would greatly lower the quality of life of future generations, this choice may not be worse for any of the people who would later live since if one had chosen the other policy, these people would never have existed. Parfit here challenges the deeply held view that moral arguments should appeal to the interests of all of the affected people. Parfit argues that it is hard to avoid what he calls the Repugnant Conclusion, or the view that compared with the existence of billions of people whose quality of life is very high, it would be in itself better if there existed some much larger number of people whose lives would be barely worth living. Parfit also presents the Mere Addition Paradox, in which various plausible assumptions are shown to lead to a contradiction. These arguments profoundly challenge deep beliefs about moral and practical reasoning.

At the time of the writing of this entry, Parfit was completing a second book Climbing the Mountain that will be about Kant's ethics, contractualism, and consequentialism. In discussing Kant's Formula of Humanity, Parfit argues that although one should not regard other people merely as a means, whether one is acting wrongly never depends on whether one is treating people merely as a means. Parfit defends Kant's claim that one must never treat people in ways to which they could not rationally consent. He then argues that if one revises Kant's Formula of Universal Law and appeals to a view about rationality and reasons that is not desire based but value based, Kant's formula can provide the best version of contractualism.

On the standard moral map, there are two main kinds of systematic moral theory. One kind is consequentialist, with utilitarian theories as the best-known examples. The other kind is Kantian theories and various forms of contractualism, which are often presented as the main systematic alternative to all forms of consequentialism. This map, Parfit argues, should be redrawn. Of the different ways of thinking about morality, it is Kantian and contractualist theories that do most to support consequentialism. Kantians, contractualists, and consequentialists ought to conclude that, in John Stuart Mill's metaphor, they have been climbing the same mountain on different sides.

Parfit also argues that Kantian and contractualist theories should take less ambitious forms. These theories should be presented not as accounts of wrongness or of moral reasoning but as claiming to describe a higher-level property that can make acts wrong, under which ordinary wrong-making properties can be subsumed. There are, moreover, several kinds of wrongness; and the most important questions are not about wrongness, but about reasons.

Parfit believes that the best way to respond to skepticism about the possibility of ethical progress is to make some. Perhaps as much as any philosopher in the last 100 years, he has done so.

See also Ethics; Kant, Immanuel; Metaphysics; Rawls, John; Thinking.


Rawls, J. A Theory of Justice. Cambridge, MA: Harvard University Press, 1971.

works by parfit

Reasons and Persons. Oxford: Oxford University Press, 1984.

"Overpopulation and the Quality of Life." In Applied Ethics, edited by Peter Singer. Pp. 145154. Oxford: Oxford University Press, 1986.

"Equality or Priority?" Delivered as the Lindley Lecture at the University of Kansas, November 21, 1991. Copyright by the Department of Philosophy, University of Kansas, 1995. Reprinted in The Ideal of Equality, edited by Matthew Clayton and Andrew Williams, pp. 81126 (New York: St. Martin's Press, 2000).

"The Unimportance of Identity." In Identity, edited by H. Harris, pp. 1345. Oxford: Oxford University Press, 1995.

"Reasons and Motivation." Proceedings of the Aristotelian Society (supplement). 1997, pp. 99130.

"Why Anything? Why This?" The London Review of Books (January 22; February 5, 1998): 2427; 2225.

"Experiences, Subjects, and Conceptual Schemes." Philosophical Topics 26 (1 and 2) (1999): 217270.

"Rationality and Reasons." In Exploring Practical Philosophy, edited by Dan Egonsson, et al, pp. 1739. Burlington, VT: Ashgate, 2001.

"Justifiability to Others." In On What We Owe to Others, edited by Philip Stratton-Lake, pp. 6789. Oxford: Blackwell, 2004.

"Kant's Arguments for His Formula of Universal Law." In The Egalitarian Conscience, Essays in Honor of G. A. Cohen, edited by Christine Sypnowich, Oxford University Press (in press).

"Persons, Bodies, and Human Beings." In Contemporary Debates in Metaphysics, edited by John Hawthorne, Dean Zimmerman, and Theodore Sider. Oxford: Blackwell (in press).

works about parfit

Barry, B., et al. "Symposium on Derek Parfit's Reasons and Persons " Ethics 96 (1986): 703872.

Dancy, J., ed. Reading Parfit. Oxford: Blackwell, 1997.

Temkin, L. "Intransitivity and the Mere Addition Paradox." Philosophy and Public Affairs 16 (2) (1987): 138187.

Larry Temkin (2005)