The claim

Fix a target, meaning what the description must predict (CLAIM-152). For the dancing couple it might be the next beat’s positions. Model the joint dynamics of the candidate’s members and their surroundings, for example as a linear model of their state variables. Then:

  1. Block. The candidate is one system (TERM-049) when, with its members grouped, the interaction matrix is nearly decomposable (LIT-905). The couplings inside the group are strong and those across its edge are weak.
  2. Threshold. The gap that sets the block off clears the Occam factor (TERM-046) for that block: δ/ε > τ, with τ² the log prior-to-posterior variance ratio (CLAIM-154). Below it, the block is not worth naming.
  3. Unit. What is named is the gap-isolated block, the projector onto the pair’s joint mode, not either member or any coordinate (CLAIM-164).
  4. Duration. The form lasts while the block keeps clearing the threshold. The couple is one system for the song and two after it. Simon’s short-run independence and long-run aggregate dependence say what the boundary licenses while it holds.

This answers the owner’s “privileged nomenclature” (CLAIM-175) with a test. The name is earned when the gap beats the cost of keeping it.

How it sits with the other tests

  • Mutual entrainment (CLAIM-172) is a sufficient mark, and it says the members are peers. This claim measures strength and passes one-way drive as well. The direction of the coupling then gives the system’s architecture, peers or hierarchy (CLAIM-167). The objection that one-way drive should not pass (CLAIM-173) is rejected.
  • Reciprocal compensation (LIT-902, unread) is a perturbation test. A block that clears the threshold should also compensate. If it does not, that is evidence against this claim (defeated_if).
  • Persistence and unity are further tests. CLAIM-161 asks whether a coherence measure is conserved within the block. CLAIM-153 asks whether the block’s contexts glue. A form can clear the threshold and still fail either.
  • Otto’s notebook is not a dynamical partner. Its coupling is a write and a later read, and a block test on synchronous dynamics will not see it. The storage route (CASE-043) needs a time-lagged version of the criterion, which is not built.
  • Dynamical independence (THEORY-257, LIT-979, NOTE-791) asks only that no information flow into the coarse variable from the rest. It allows outgoing coupling and forbids incoming. Near-decomposability asks for weak coupling across the edge in both directions. A module that drives the rest and receives nothing is dynamically independent; one that is driven never is. The two pick different blocks whenever coupling is one-way.
  • Acting as a unit (THEORY-265, LIT-989, NOTE-773). In a modular coordination game the interaction matrix is nearly decomposable throughout, so the block verdict is the same before and after entrainment. What changes is timing, and with it whether the module responds to the others as one. So a block that clears the threshold need not behave as a unit. That is consistent with this claim, which disclaims agency, but it shows the two come apart in a concrete case.

What it does not say

  • That the verdict is target-free. A different target can group the members differently.
  • That a form clearing the threshold is an agent (TERM-044) or a self (TERM-045). Those are QUESTION-009 and the subject sense of ADR-024.
  • That anything has been measured. CASE-045 is the study it would need.
  • When the block stops persisting. The duration clause is stated over joint dynamics, which are estimated over an interval. For information measures the averaged verdict and the verdict at a moment can disagree in sign (THEORY-268, LIT-953, NOTE-756), so the clause needs a window and a tolerance for how many failing moments end the form. Neither is set.
  • That one threshold serves the whole system. On tangles, each region of a network has its own best order, and one global threshold splits some forms and misses others (THEORY-254, LIT-955, NOTE-814). The Occam factor here is set per block, which is the kind of per-region setting a global threshold lacks.
  • That the form makes its own boundary. The test reads the boundary off how strongly the members interact, inside the block against across its edge. A beam joining two pendulums clears it for the next swing, as a cell’s membrane does for the cell. So the test names a unit of description, and it cannot tell a boundary the form produces from one imposed on it (CLAIM-194). The individuality that minimal agency is said to need (THEORY-1119) is a further condition. That matters where CLAIM-174 takes this test as its first condition.

Note of 2026-10-19: closure without a block, and flux

A5 of the exchange of 2026-10-19 on coarse-to-fine processes asked whether “organizational unity require[s] a subsystem boundary, or can it arise from a dynamically closed collective mode distributed across multiple otherwise entangled subsystems?” Two things came of it.

  • The two tests come apart under symmetric coupling too. This claim already records that dynamical independence and the block pick different units when coupling is one-way. CLAIM-388 shows they also differ when it is symmetric. Under uniform coupling the sum of all units is exactly closed, and no grouping of the units is a block (CASE-120). The unit named here is already a mode (point 3, after CLAIM-164), but it is found by grouping members. Whether a mode found without a grouping can be one system is QUESTION-218. A case of it that compensated and entrained would meet this claim’s defeated_if.
  • A third kind of organization. A5 set containment (this claim’s block) and mode (closure) beside flux: a pattern of transfer that persists while constituents are replaced. In turbulence, transfer across scales is local without the scales being weakly coupled blocks (Eyink and Aluie, LIT-1239, unread). Whether flux picks out units this test misses is QUESTION-219. A5’s guard is this claim’s: a newly found mode or flux “should not automatically be treated as an individual, much less an agent.”

Note of 2026-10-20: what the readings did to the block test

The first readings of the coarse-to-fine program bear on this claim in four ways. None changes the criterion.

  • Weak coupling in, little dependence. For a block’s full state in a linear Gaussian VAR(1), dynamical dependence is of second order in the coupling into the block, whatever the coupling out of it (CLAIM-390). So a block that clears this claim’s test because its incoming coupling is weak is also nearly closed in Barnett and Seth’s sense. A block that clears it with strong outgoing coupling and weak incoming coupling is too. That is the one-way case this claim already passes (CLAIM-167).
  • The aggregate is another matter. The sum over a block closes only if the block’s own dynamics close on it. In one step that needs equal column sums within the block (CLAIM-386). Simon’s argument relies on the fast transient to make the rest small. The unit this claim names, the projector onto the block’s joint mode (point 3), is the right object for that reason: it is the slow part of the block, not its sum.
  • Read the gap spectrally. Shpak, Stadler, Wagner and Altenberg’s flat landscape (NOTE-977) has entrywise weak coupling between blocks and no separation of time scales at any rate. This claim’s test compares a gap against coupling, so it is already the spectral reading, which is the one that works.
  • Groupings that close without being blocks. Column-equitable partitions (THEORY-755) and turbulent scale bands (THEORY-754, conditional) organize a system without a gap. Whether either is “one system” is QUESTION-218 and QUESTION-219.
  • A data-driven gap gives the block, not its duration. Nadler et al. (NOTE-986) recover the wells of a double-well diffusion from equilibrium samples almost perfectly (99.6–99.8% of points). But they underestimate the slow eigenvalue that sets the wells’ lifetime by 30–80%, because few samples cross the barrier. This claim’s duration clause needs a lifetime, and equilibrium data are the weak place to get one.

Note of 2026-10-27: pressures from the dynamics of transitions

A14 of the exchange of 2026-10-27 raised three pressures on criteria that read an individual off a gap. They are filed as QUESTION-281, not as objections, since none is shown to defeat this claim’s coupling-gap criterion. (i) Non-normal transient growth can carry a system out of a regime whose linearization is stable at every instant (THEORY-724; LIT-932). (ii) Rate-induced tipping can end a form whose frozen-parameter attractor still exists (LIT-1654, unread), which bears on “it lasts as long as that block persists”. (iii) Localized structures persist as dynamical individuals while their material turns over (LIT-1642, unread), a case for testing whether the criterion follows a form through turnover.

Note of 2026-10-27 (later): the pressures read

Two of the pressures noted above are now read. In Ashwin et al.’s model the matrix M is the same at every instant (their eq. 4), so a gap or spectral verdict computed from frozen dynamics stays constant through the tip (NOTE-1215). Read on frozen dynamics, “it lasts as long as that block persists” would say the form lasts after the system has left it; the clause survives if “persists” is read on the trajectory. In Toner and Tu’s theory (NOTE-1228) the order is a gapless mode of a field, stabilized by neighbourhoods that keep changing, so no fixed grouping of members persists while the order does. It is a case for QUESTION-218, a mode found without a grouping.

Note of 2026-10-29: the narrowed rule

CLAIM-154 now holds only where the candidate’s model stays regular at its switch-off. Where it is singular the rule overcharges (CLAIM-188), so a candidate it rejects may still earn a name.

Note of 2026-10-29: what holds it back

Its defeated_if makes clearing the threshold necessary for one system, not only sufficient, and that half is unanswered. CLAIM-388’s closed mode has no block, Toner and Tu’s flock (NOTE-1228) keeps its order while no grouping of members persists, and the notebook’s coupling needs the time-lagged test QUESTION-116 asks for; whether any of these is one system is QUESTION-218, and a yes would meet the defeated_if. The duration clause also has no window or tolerance, and it holds only if “persists” is read on the trajectory (NOTE-1215).