Derek Parfit

Agora

Derek Parfit

1942–2017

A first way ina deliberate simplification – the portrait says more

Personal identity over time is not what matters – and seeing this makes us care more about others and fear death less.

Placement

Analytic Philosophy · East Asia · Ethics, Existence & Self

Reasons and Persons: personal identity is not what matters.

Key ideas

Reductionism about persons
Repugnant Conclusion

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Influence

Influenced by 4

Siddhartha Gautama (Buddha)

influenced by
Parfit added an appendix “Buddha’s View” to Reasons and Persons (1984), quoting Buddhist texts to show that the Buddha had held the reductionist view of persons he defends. D. Parfit, Reasons and Persons (1984), Appendix J “Buddha’s View”
Evidence: AI draft
Siddhartha Gautama (Buddha) › c. 480–400 BCE · conventionally dated 563–483 BCE
John Locke

influenced by
Parfit developed Locke’s memory criterion into psychological continuity – overlapping chains of memories, intentions and character – and asked whether identity is what matters (Reasons and Persons, 1984). D. Parfit, Reasons and Persons (1984); J. Locke, An Essay concerning Human Understanding (2nd ed., 1694), “Of Identity and Diversity”; SEP “Locke on Personal Identity”
Evidence: AI draft
John Locke › 1632–1704
David Hume

influenced by
Parfit’s reductionism about persons – identity is psychological and physical continuity, no further fact – is commonly compared with Hume’s bundle view (Reasons and Persons, 1984). D. Parfit, Reasons and Persons (1984); D. Hume, A Treatise of Human Nature (1739–40), “Of personal identity”; SEP “Personal Identity”
Evidence: AI draft
David Hume › 1711–1776
Henry Sidgwick

influenced by
Parfit took up Sidgwick’s ‘dualism of practical reason’ between egoism and impartial benevolence and sought to resolve it (Reasons and Persons, 1984; On What Matters, 2011). D. Parfit, Reasons and Persons (1984); On What Matters (2011); H. Sidgwick, The Methods of Ethics (1874); SEP “Henry Sidgwick”
Evidence: AI draft
Henry Sidgwick › 1838–1900

Influenced 2

Nick Bostrom

influenced
Bostrom used Parfit’s comparison of a war killing 99 per cent of humanity with one killing everyone to argue that reducing existential risk is a global priority (2013). N. Bostrom, “Existential Risk Prevention as Global Priority”, Global Policy 4 (2013); D. Parfit, Reasons and Persons (1984)
Evidence: AI draft
Nick Bostrom › b. 1973
William MacAskill

influenced
MacAskill built on Parfit’s population ethics, including the repugnant conclusion and the value of future generations, in his case for longtermism (What We Owe the Future, 2022). W. MacAskill, What We Owe the Future (2022); D. Parfit, Reasons and Persons (1984)
Evidence: AI draft
William MacAskill › b. 1987

Criticism

Criticizes 1

Bernard Williams

criticised
Parfit rejected Williams’s view that all reasons are internal, grounded in motivations: reasons are given by facts that count in favour of acting (On What Matters, 2011). D. Parfit, “Reasons and Motivation”, Proceedings of the Aristotelian Society, suppl. 71 (1997); On What Matters (2011), vol. 1; B. Williams, “Internal and External Reasons” (1980)
Evidence: AI draft
Bernard Williams › 1929–2003

Works

1984Reasons and Persons
Teleportation, fission – personal identity is not what matters.
2011On What Matters
Kantians, consequentialists and contractualists “climbing the same mountain”.

Position

In Reasons and Persons Parfit used thought experiments involving teleportation and brain division to argue that personal identity is not a deep further fact. A person is nothing over and above a body, a brain and psychological connections such as memory and character. What matters is this psychological continuity, which comes in degrees – and Parfit found this liberating, as the wall between himself and others became thinner. Its last part became a starting point of population ethics. There Parfit showed that principles which seem plausible imply the “Repugnant Conclusion”: for any population of people who all live very good lives, a much larger population whose lives are barely worth living would be better. The conclusion follows from premises that are hard to reject, yet it strikes most people, Parfit included, as unacceptable; he spent decades looking for a way out. His late work On What Matters argued that Kantians, consequentialists and contractualists are “climbing the same mountain on different sides.”

Life & context

Parfit was born in 1942 in Chengdu, China, to British medical missionaries and grew up in Oxford. He first studied history before turning to philosophy. Almost his entire career was spent at All Souls College, Oxford, with regular visiting positions at Harvard, New York University and Rutgers. He was famous for working on his books with extreme perfectionism for many years.