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Derek Parfit

Analytic · Europe · 1942 to 2017

British philosopher who argued that who we are over time matters less than we think. He also argued that some moral truths hold whatever anyone believes.

What it is

Derek Parfit (1942 to 2017) was an English philosopher, born in Chengdu, China, to parents who were both doctors. His work on ethics, personal identity and the nature of reasons was widely influential from the 1980s, and many of his peers considered him the most important moral philosopher of the late twentieth and early twenty-first centuries.

He studied modern history at Oxford before turning to philosophy during a fellowship in the United States, and he spent most of his career as a research fellow at All Souls College, Oxford. His two great books are Reasons and Persons (1984) and On What Matters, which he wrote over some fifteen years.

The main ideas

  • There is no extra self. Following Hume, he argued that there is no unique entity, a self, beneath the stream of experiences and dispositions that we attribute to one person.
  • Identity is not what matters. It is possible to survive without being the same person as anyone later, so what matters in survival is psychological continuity and connection, not strict identity.
  • Our duties to later people. He used these ideas to ask what we owe to future generations, and he put forward the Repugnant Conclusion as a problem for theories of how many people there should be.
  • One mountain, three sides. In On What Matters he argued that consequentialism, Kantianism and contractualism, rightly improved, can be combined into a single view he called the Triple Theory.

What it looks like in practice

Picture someone who is told that a machine could copy them exactly and then destroy the original, and who is asked whether they would be dying. Parfit would invite them to see that the fear rests on a view of the self that may be mistaken, and that what they care about, a continued life with their memories and concerns, would carry on. This is an illustration of the idea, not a quotation.

Books and moments

  • Reasons and Persons (1984) is his first book and made him famous. It covers personal identity, rationality and ethics.
  • On What Matters is his second major work, circulated in draft to hundreds of colleagues, with the final volume published after his death.

Questions and criticism

  • Is the self an illusion? His claim that there is no deep further fact about identity has been defended and also resisted by those who think it leaves out something about persons.
  • Can the three ethical traditions be joined? The Triple Theory is admired for ambition, and critics ask whether the traditions really agree or only appear to once reshaped.
  • Is the Repugnant Conclusion a real objection? Many theories of population lead to it, and whether it should be accepted or avoided is still debated.

Close neighbours

He drew on Hume's view of the self and on Kant and the utilitarians. The pages on Hume, Kant, Sidgwick and Singer show the thinkers around his work.

Written by epchē in our own words, and checked against independent sources on 9 October 2026. The sources are listed below.

Who they connect to

Influenced

  • Peter Singer · Singer has cited Parfit's arguments on impartial morality. (scholars disagree about this link)

Influenced by

  • David Hume · Parfit's reductionist view of persons follows Hume's bundle theory of the self.
  • Henry Sidgwick · Parfit called Sidgwick the greatest of the modern moral philosophers and built on his arguments.

Reacted against

  • John Locke · Parfit developed his puzzle cases as a challenge to Locke's memory account of identity.

Runs parallel to

  • Siddhartha Gautama (the Buddha) · Parfit argued that a person is nothing over and above a stream of connected events. He wrote that the Buddha would have agreed.

Other Analytic thinkers

Sources we used

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