Derek Parfit

Key ideas

In Reasons and Persons, Parfit used thought experiments, including the teleporter, brain division and gradual replacement, to argue that personal identity is not a deep further fact. It consists in psychological continuity and connectedness, which can hold to different degrees and can even branch. In some cases the question 'Would it be me?' has no answer, and that need not trouble us.

His conclusion was that identity is not what matters in survival. What matters is the continuation of memories, intentions and character, however caused. He wrote that accepting this made the wall between himself and others seem to dissolve, and made him less concerned about his own death. The view shapes personal identity, mind uploading and the no-self view.

He also transformed population ethics, discovering what he called the Repugnant Conclusion, and in his last work argued at length that there are objective moral truths, contributing to moral realism.

Life, briefly

Parfit was born in China to medical missionary parents and grew up in Oxford. He spent his entire academic career at All Souls College, Oxford, and was famous for working almost without pause. He was also a serious architectural photographer, returning again and again to Venice and St Petersburg.

Major works

• Personal Identity (1971)
• Reasons and Persons (1984)
• On What Matters (2011, 2017)

Further reading

• WikipediaDerek Parfit