Summary

This post introduces the Identity Horizon: a structural measure of how quickly a choice causes the living population set to be replaced by a different set. It doesn’t measure moral importance, harm, or value—only population replacement speed via living-population overlap decay between divergent futures. Key insight: all non-null choices cause immediate population divergence (conception, survival, interaction are timing-sensitive and socially entangled), but spread rates differ. Serial propagation (mate choice) affects small lineages spreading outward slowly; parallel propagation (wars, pandemics) affects many lineages simultaneously, dropping overlap rapidly. A choice is null only if alternatives are symmetric and decoupled from population-affecting systems at the tracked pattern level (sock order yes, tea vs coffee no—caffeine affects timing/behavior coupling into reproduction networks). The concept is deliberately blind to experience/outcome differences among the same people, tracking only who exists. Primary use is diagnostic: ruling out invalid arguments relying on “future people” as stable object of concern. Under strict identity criterion, future populations are fragile and rapidly replaced—formal expression of Non-Identity Problem.

Key Concepts

  • Identity Horizon – Time until living-population overlap between divergent futures falls below threshold (typically 1%).
  • Living-population overlap – Fraction of living people composed of same individuals in both futures; decays toward zero.
  • Immediate divergence norm – All non-null choices cause immediate population divergence via timing-sensitive conception/survival/interaction.
  • Null vs trivial – Choice is null only if alternatives symmetric and decoupled from population systems; subjective triviality irrelevant.
  • Serial vs parallel propagation – Serial (mate choice) spreads slowly through lineages; parallel (wars) affects many simultaneously.
  • Replacement vs experience – Tracks who exists, not what happens to them; blind to state divergence among same people.
  • Pattern-relative nullity – Null at population-identity grain, not microphysical; may have extremely long horizons rather than infinite.
  • Non-Identity Problem formalization – Future populations rapidly replaced; “preserving future people” incoherent under strict identity.

Evolution Notes

  • Provides formal grounding for discussing “impact” without conflating different meanings (mattered, caused harm, changed history).
  • Connects to QBU (branching) framework: branching cheap, population replacement measurable.
  • Diagnostic tool rather than normative framework: doesn’t answer should-questions but clarifies what’s being discussed.
  • Example (Hitler’s parents) shows distinction between replacement speed and latent causal leverage.
  • Makes explicit fragility of future-person identity under choice perturbations.

Tags

Cross-References

Open Questions

  • How should ethics accommodate rapid identity replacement if “preserving future people” is incoherent under strict identity?
  • Can identity horizon inform policy decisions without collapsing into paralysis (if all choices replace populations)?
  • What grain of identity tracking is appropriate (strict biological vs functional vs experiential continuity)?
  • Do identity horizons differ systematically across choice types in ways that matter morally?
  • How does this interact with multi-world ethics in QBU framework—should we care about population identity across branches?
  • Is there a minimal identity-stability requirement for meaningful optimization targets, or does ethics need to abandon person-identity grounding?