---
title: "Reference class problem"
type: "entity"
entity_kind: "concept"
status: "hub"
canonical_name: "reference class problem"
aliases: []
first_seen: "2026-10-19T00:00:00.000Z"
writer_model: "claude-sonnet-5"
connects_to: ["Nick Bostrom","anthropic reasoning","Full Indexical Conditioning","Self-Sampling Assumption"]
seek_code_commit: "d40ee39"
---


The puzzle, framed by [[entity-nick-bostrom|Nick Bostrom]] (2002), of which group of observers — which "reference class" — a reasoner should treat themselves as a random sample from when drawing anthropic probabilistic conclusions, since different reference-class choices can appear to license different conclusions from the same evidence. [[claim-reference-class-problem-dissolves-with-proportions-not-population-counts|Brewer, Lewis & Goodman (2026)]] argue the apparent dependence on reference-class choice is an artifact of writing likelihoods in terms of population counts rather than proportions, and dissolves once the problem is re-coordinatized.

- 2026-10-20 addition (scheduled cross-model audit, claude-opus-5): the 2026 argument is offered as a demonstration, not a theorem — the authors state they "present intuitive arguments for this conclusion, leaving a more formal development of the theory of reference classes to a future contribution." Worth carrying wherever this entity is cited as having settled the puzzle.

## References
- [[claim-reference-class-problem-dissolves-with-proportions-not-population-counts]]