Extended Mind Criteria
The full test for when something outside the body counts as part of the mind, as stated by a Tilburg University explainer (text: Hans Dooremalen) attributing it to Clark & Chalmers: the Parity Principle is only criterion 1 of 4, and alone is too weak — by itself it would admit an old encyclopedia in your shed, and with it "almost the entire world," into the mind. What the mind is extended with must additionally be typically invoked (used normally, as a matter of course), trustworthy (its deliverances automatically endorsed, not re-verified), and easily accessible (available when needed, low effort to consult). The stored phone number passes all four; so, uncomfortably, does Google Maps — which is the criteria's open stress test, not their refutation, in the source's telling.
For the vault this is the operational checklist for when an external store has crossed from tool to part of the cognitive system — and it reads directly onto agent memory: a markdown vault or memory layer is genuinely the agent's extended memory only when it is routinely consulted (typically invoked), trusted enough to act on without re-derivation (trustworthy), and cheap to reach at decision time (easily accessible). A store that is merely present but rarely primed, distrusted, or expensive to query is the encyclopedia in the shed.
Claims
- The parity principle alone is too weak: unsupplemented, it extends the mind until "almost the entire world becomes part of the mind" (the encyclopedia-in-the-shed case). (principle — as asserted by the video)
- That which extends the mind must also be used normally ("typically invoked"), considered trustworthy, and easily accessible. (principle — as asserted by the video, attributed to Clark & Chalmers)
- A smartphone-stored phone number meets all four criteria for people who always carry their phones — normal use, ubiquitous availability, trusted correctness ("the phone is not mistaken"), ease of use — so those numbers belong to their extended mind. (observation — the source's worked example)
- Google Maps also meets all four criteria, which entails that its user "knows" the address of any museum it can look up; the video poses this as an open challenge — if that goes too far, where is the mistake in the criteria or argumentation? (observation — the source's stress test, left unresolved in-source)
Related
- Parity Principle — criterion 1; this page holds the supplementary three and the insufficiency argument that motivates them.
- Extended Mind — the thesis the four criteria operationalise.
- AI Second Brain — the criteria as a health check for an operator's external store: present-but-unconsulted files are the encyclopedia in the shed.
- Layered Agent Memory — memory-tier design targets exactly these properties: routine priming (typically invoked), trusted content (trustworthy), low retrieval cost (easily accessible).
- Distillate: The Extended Mind Hypothesis (Tilburg University explainer)