# Derek Parfit **Domain:** Philosophy / Personal Identity / Ethics **Doc Type:** Thinker Node **Classification:** Adversarial Identity Bench **Maturity:** Foundational **Related:** [[wiki/Personal Identity|Personal Identity]], [[wiki/Psychological Continuity|Psychological Continuity]], [[wiki/Fission and Fusion of Persons|Fission and Fusion of Persons]], [[wiki/Identity Is Not What Matters|Identity Is Not What Matters]] --- ## Position **Derek Parfit** developed a reductionist account of personal identity in which the facts about a person's persistence consist in physical and psychological relations rather than a further indivisible fact about a soul or Cartesian ego. His fission cases make the pressure visible: two future people may each preserve the relevant memories, intentions, character and causal continuity of one earlier person even though numerical identity cannot be one-to-two. Parfit called the practically important relation **Relation R**: psychological connectedness and continuity with the right kind of cause. The radical consequence is not that persons are unreal or disposable. It is that survival, responsibility and rational concern may track degrees and relations that do not coincide perfectly with numerical identity. ## Consequence for Continuity Architecture Parfit supplies both support and opposition. A continuity system may preserve much of what matters even when it cannot prove strict identity. But it must not quietly rename that practical survival as numerical identity. Forks may deserve standing because they inherit Relation R while remaining distinct claimants. The architecture therefore needs separate predicates for lineage, psychological continuity, legal succession and identity. ## Sources - [Stanford Encyclopedia of Philosophy — Personal Identity](https://plato.stanford.edu/entries/identity-personal/) - Derek Parfit, *Reasons and Persons*, Part III (Oxford University Press, 1984). ## See Also [[wiki/Teletransportation Paradox|Teletransportation Paradox]] · [[wiki/Closest Continuer Theory|Closest Continuer Theory]] · [[wiki/Fork Rights|Fork Rights]] · [[wiki/Successor Standing|Successor Standing]]