Why Preserved Structure Recurs Across Theory Change: Preconditions for Persistence and Premises for Conservation

From Worrall's continuity thesis to Ladyman and Lorenzetti's effective ontic structural realism, realist commitment centers on structures that recur across theory change. The tradition leaves open why they recur: which constraints persistence-tracking requires, and which depend on conditions successor theories may not retain. I argue that recurrence has two sources. First, a non-vacuous claim that the same token persists across successive registrations requires a correspondence distinguishing continuation from replacement. Formally, a correspondence not preserved under independent relabeling strictly reduces the symmetry of the complete tracking structure. In the maximally symmetric case, where registrations distinguish no tokens internally, the correspondence carries the asymmetry tracking requires. This gives a constitutive analogue of Curie-style reasoning without causal or dynamical content. Second, conservation is conditional. At full capacity under a fixed finite budget, admissions and relinquishments balance at every transition. Under pressure with fixed admissibility, departures also exclude coherent return. A countermodel nevertheless combines pressure, exact re-identification, and unbounded operative growth, so persistence under pressure does not entail conserved capacity. The balance is structural accounting; it yields no Noetherian conservation law. Physical application requires independent warrant for mapping operative capacity to a physical quantity and for premise attribution at fixed units, referent, and scale. Thus every successor theory engaged in persistence-tracking must distinguish continuation from replacement; conservation-like constraints recur only where their enabling premises survive.