Prior treatments of identity in this framework characterize closure as a threshold condition and the Invariance Maintenance Condition (IMC) applies from the moment closure obtains. Neither treatment addresses the structural event of crossing: what has to become true about a configuration's local dynamics for it to enter the regime in which maintenance dynamics are admissible inputs to the constraint they maintain. This paper introduces Closure Activation as that structural transition. Activation marks the first admissible instantiation of recursive constraint enforcement — the point at which a configuration's own maintenance dynamics become defined over its own state and act to enforce constraint satisfaction under admissible transformation. Admissibility is defined independently of duration: persistence is not part of the definition of activation but a subsequent property of trajectories that remain within the admissible regime over time. Activation establishes that closure is possible; closure names the regime in which that possibility is sustained under perturbation and cost. Three conditions are jointly necessary for activation: the governing constraint must be state-referential, the corrective response must be internally funded, and the maintenance budget must be cost-viable. These are not independent requirements; they are three aspects of a single structural change. The paper introduces a tripartite classification of configurations — closed, closure-competent, and subthreshold — as its primary contribution. Prior frameworks collapse the latter two into a single non-identity category. This paper argues they are structurally distinct: closure-competent configurations achieve admissible instantiation of recursive constraint enforcement but cannot sustain the funding required to maintain it; subthreshold configurations lack an admissible mapping between maintenance dynamics and constraint enforcement entirely. The flicker phase — the interval between first recursive closure and stable regime entry — is a structurally predicted feature for configurations approaching the viability threshold from below, not a measurement artifact. Perturbation is the necessary diagnostic instrument: the three classes are not distinguishable at rest. The paper explains why the IMC's four conditions are jointly satisfied at activation or not at all, and states falsification conditions with expected empirical signatures.
Charles S. Thomas (Sun,) studied this question.