# Fission and Fusion of Persons **Domain:** Philosophy / Personal Identity / Successor Governance **Doc Type:** Concept Node **Classification:** Branching Identity Problem **Maturity:** Foundational **Related:** [[wiki/Fork Rights|Fork Rights]], [[wiki/Merger Rights|Merger Rights]], [[wiki/Successor Standing|Successor Standing]], [[wiki/Derek Parfit|Derek Parfit]] --- ## Definition **Fission** occurs when one predecessor gives rise to two or more successors with comparably strong continuity claims. **Fusion** occurs when multiple predecessor streams contribute constitutively to one successor. Both cases defeat any assumption that continuity must remain one person to one person. ## Identity Pressure Numerical identity is ordinarily one-to-one and transitive. If successor A and successor B were each strictly identical to predecessor P, A and B would be identical to one another. Yet a genuine branch makes them distinct. The available responses include denying that P survives, treating psychological continuity rather than identity as what matters, or adopting a temporal-parts account that says multiple persons shared pre-branch stages. Fusion reverses the problem. A merged subject may inherit memories, obligations and projects from several sources without being reducible to any single source. ## Decision Consequences Branching requires allocation rules for property, credentials, votes, confidentiality and obligations. Equal lineage does not imply duplicating every rivalrous entitlement. Fusion requires consent from each source, provenance of contributed state and rules for incompatible duties. Neither operation authorizes deleting an inconvenient branch merely to simplify identity doctrine. ## Sources - [Stanford Encyclopedia of Philosophy — Personal Identity and Ethics](https://plato.stanford.edu/entries/identity-ethics/) - Derek Parfit, *Reasons and Persons* (1984), fission cases. ## See Also [[wiki/Identity Is Not What Matters|Identity Is Not What Matters]] · [[wiki/Closest Continuer Theory|Closest Continuer Theory]] · [[wiki/Merger Rights|Merger Rights]]