Two traditions agree that things persist and disagree about why. The classical theist holds that no contingent thing keeps itself in being for an instant: existence must be conserved, moment to moment, by a being that holds it there, on pain of annihilation. The existential-inertia theorist denies the dependence: a thing that exists tends to remain in existence on its own, absent a sufficient destroyer, and needs no concurrent sustainer to persist. This book sides with the inertialist's conclusion and rejects the inertialist's ground. Nature is not held in being by anything outside it; there is no concurrent divine sustainer to invoke. But neither does it persist by brute default. It persists because Φ (the retention of identity across an interval) is what persistence consists in. The conservation debate is conducted over a gap the structural account closes from below.

The conservationist case is Thomist in origin. Aquinas holds that God's causality is required not only to bring things into being but to keep them there: creatures stand to God as the air stands to the sun's illumination, ceasing the instant the influx ceases (*ST* -(Aquinas, Thomas, (1265–1274) 1947), I.104.1; *De Potentia* -(Aquinas, Thomas, (1265–1266) 1932), q.5 a.1). Freddoso ("God's General Concurrence with Secondary Causes," -(Alfred J. Freddoso, 1991); and the 1994 sequel -(Freddoso, Alfred J., 1994)) reconstructs the medieval taxonomy, mere conservationism (God conserves things in being but creatures produce their own effects), concurrentism (each created effect is produced by God and creature together), and occasionalism (God is the only real cause, creatures mere occasions for his acting), and defends the concurrentist reading on which divine sustaining is required for every created effect. Feser (*Aquinas* -(Feser, Edward, 2009); *Five Proofs of the Existence of God* -(Feser, Edward, 2017)) presses the demand through act and potency: a thing's existing at each moment is a potency that must be actualized by something already actual, terminating in Pure Act. Against the demand stands the existential-inertia thesis. Beaudoin ("The World's Continuance: Divine Conservation or Existential Inertia?" -(Beaudoin, John, 2007)) and, in its most developed form, Schmid ("Existential Inertia and the Aristotelian Proof," -(Schmid, Joseph C., 2021)) and Schmid and Linford (*Existential Inertia and Classical Theistic Proofs* -(Schmid, Joseph C.; Linford, Daniel J., 2022)) argue that persistence is the default state of concrete objects and that the conservationist owes a positive argument the tradition has not supplied. Kvanvig and McCann ("Divine Conservation and the Persistence of the World," -(Kvanvig, Jonathan L.; McCann, Hugh J., 1988)) hold the conservationist line with the sharpest form of the counter-challenge: what grounds a thing's continuing to exist from one moment to the next, they ask, if not a sustaining cause? The structural account answers that question without adopting either side's location for the ground.

*First.* The conservationist argument runs on a hidden premise: that continued existence is a kind of change, a fresh actualization at each moment, a coming-to-be repeated. Feser's act/potency version makes the premise explicit: existence-now is a potency, and a potency requires a concurrent actualizer. Grant the framework and the conclusion follows; the demand is only as strong as the premise that persistence is a transition. It is not. A transition is a passage from one state to another. Mere continued existence need not be a fresh transition, although a persisting thing may undergo many qualitative changes while remaining the same thing. The conservationist must therefore argue that existing at a later time is a continuously derived effect, not simply infer that persistence as such is the absence of all change. The act/potency machinery earns its concurrent cause where there is becoming to account for; applied to mere continuation it manufactures a becoming that is not there and then requires a cause to sustain the manufactured becoming. Continuation is not continuous becoming. Nothing crosses from potency to act in a thing's simply remaining what it is, and so nothing is required to drive the crossing. The sun-and-illumination analogy (*ST* -(Aquinas, Thomas, (1265–1274) 1947), I.104.1) imports exactly this picture (a continuous effect requiring a continuous cause) and holds only if continued being is an effect of the relevant kind. Illumination is a process; existence is not. (The simultaneous-causation machinery the Thomist offers to make the sustaining concurrent rather than prior is taken up at [§5.1.3](<5.1.3 Simultaneous Causation.md>); the point here is upstream of it: there is no sustaining-effect to make concurrent.)

This defeats the act/potency form of the demand, but not every form of it. The concurrentist need not say that persistence is a becoming at all. Freddoso's continuous-creation reading (-(Alfred J. Freddoso, 1991); -(Freddoso, Alfred J., 1994)) treats created existence as a continuously-derived *effect*: dependent at every instant on a sustaining cause, yet with no transition, nothing crossing from potency to act, no becoming to drive. So construed, the demand never leans on the transition premise and survives its denial, but it survives as a demand for a *ground*, in virtue of what the thing exists now, not for a cause of change, and a grounding demand is met below rather than here. Two replies converge on it. The ground the concurrentist places in an external sustainer is supplied one level down by Φ (third move): once continued existence has a structural analysis, a continuously-deriving sustainer is not thereby shown redundant. Excluding the sustainer requires an additional argument that the constitutive account exhausts the relevant explanatory demand. And independently, as Chapter 6 will argue ([§6.1](<6.1 Greatness.md>)), no candidate is available to do that work: a being answering to the classical specification (atemporal, aspatial, immaterial) is ∅ under that description and could derive nothing, so even a sound continuous-derivation demand would have nothing to name as the deriver. The transition form fails here; the continuous-effect form is answered downstream, not waved past.

*Second.* Conceding that persistence is not a transition does not end the matter, and the most precise opponent presses past it. Schmid's question is not "what changes a persisting thing?" but "in virtue of what does it persist rather than not?", a demand for a ground, not for a cause of change. Schmid and Linford (-(Schmid, Joseph C.; Linford, Daniel J., 2022)) are right that the demand cannot be waved off: a thing's continuing to exist is a fact about it, and facts about what is have grounds. The existential-inertia theorist who answers "it just does: persistence is the default" has named the explanandum (the fact to be explained) and called it an explanation. The structural account does not take that exit. Φ provides a constitutive analysis of persistence: persistence consists in the relevant retention or continuity of identity across an interval ([§2.6](<2.6 Triconditionality of Nature.md>)). That answers what persistence is. It does not, merely by definition, answer the conservationist's distinct explanatory question of why this particular thing continues rather than ceases; treating the constitutive analysis as a sufficient sustaining explanation would beg that question. This is deeper than any contingent disposition the object carries (deeper than a tendency-to-persist that might be present or absent, masked or triggered) because Φ is the condition under which the object is a determinate something at all, at either moment. The conservationist is right that persistence is grounded and not brute; the inertialist is right that the ground is not God. Both put the ground outside the persisting thing: the theist in a sustaining cause, the inertialist's critics in a missing one. It is one level down, in the structural condition any persisting thing already instantiates by being a thing across time. This is the book's inversion performed at the site of conservation: the feature the tradition reaches for (a sustaining ground beneath contingent existence) is real, and is not what the tradition takes it to be.

*Third.* Schmid's modal-collapse instinct supplies the sharpest reply available to the opponent. If persistence is grounded in Φ, and Φ is necessary (the book argues exactly this) then is the persistence of every particular thing necessary too? If the ground cannot fail, and the ground is what holds the thing in being, then the thing cannot fail to persist, and the contingency of the world collapses into necessity. The worry is the existential-inertia analogue of the modal-collapse argument Schmid presses against divine simplicity, and it is the one objection a structural ground must answer or forfeit the field.

It does not go through, and the reason is a distinction the book has already drawn. The necessity of Φ is the necessity of the condition (that whatever persists does so by retaining identity across an interval), not the necessity of any particular persister's retaining it. The level-distinction is fixed at [§2.8.4](<2.8.4 Necessity Precedes Contingency.md>): that the conditions of contingency are necessary does not make the contingent facts they condition necessary; the framework within which things come and go cannot itself come or go, while the things within it still do. L9, the non-propagation of constitutive grounding ([§4.4.9](<4.4.9 Modal Collapse Objection.md>)), is the grounding-theoretic statement of that same distinction rather than a second defense: a constitutive ground hands its modal status to the *condition* it grounds, never to the particular actualizations that satisfy it. L9 is earned at [§4.4.9](<4.4.9 Modal Collapse Objection.md>) for the necessity of change: there □(T∧S∧Φ) and □◇C are not ground and grounded but one fact under two readings, so the necessary possibility of change carries its necessity by identity, not by transmission across a grounding relation. What the conditions ground *constitutively, not productively* are the particular changes, with the necessity propagating to none of them (□◇C, not □C). The persistence case runs that constitutive half of the schema once more, with one shift worth marking: at [§4.4.9](<4.4.9 Modal Collapse Objection.md>) the constitutive ground bears on each particular change, whereas here it bears on persistence under a constitutive *condition*, leaving the contingent de re fact (*that any particular thing persists*) outside the reach of the necessity.

Φ grounds persistence *constitutively*, not productively: it does not produce each thing's continuation as an effect produces its output, which is the only way necessity would propagate Spinoza-fashion; it is what continuing-to-be *consists in*, the identity-retention condition any persister instantiates simply by being a thing across the interval.

So the □ attaches to the conditional, read de dicto (a claim about the proposition, not the thing), □(if x persists, x persists by Φ): necessarily, whatever persists does so by retaining identity across an interval. It does not attach to the de re □(x persists): no particular thing's continuing is thereby made necessary. Φ's being necessary no more makes this oak's persistence necessary than the necessity of the conditions of value makes any particular thing valuable of necessity. The oak persists by Φ while it persists, and ceases when its identity-retention fails. Modal collapse is blocked not at two joints but at one stated twice: the level-distinction of [§2.8.4](<2.8.4 Necessity Precedes Contingency.md>) and L9 of [§4.4.9](<4.4.9 Modal Collapse Objection.md>) are the same non-propagation seen from the side of levels and from the side of grounding.

*The nearest neighbors.* Three positions also locate persistence in what the thing is, and the account must not blur into any of them. Dispositional essentialism grounds persistence in a first-order power to persist: a disposition the object carries, one that could be present or absent, masked or triggered. Φ is not such a power: a disposition is a further feature of an already-individuated thing, whereas Φ is the condition under which there is an individuated thing at all, at either end of the interval, to bear features.

Beaudoin's naturalist inertia (-(Beaudoin, John, 2007)) reaches the right conclusion (no sustainer) by treating persistence as a brute default; it differs from the structural account exactly as the brute inertialist of the second move does, by leaving ungrounded what the structural account grounds.

And Spinozist necessitarianism grounds persistence in the necessity of substance, paying for it with the collapse just blocked: it runs the ground's necessity straight into the persister, making every continuation necessary. The structural account takes the necessity of the ground together with the level-distinction, so the ground is necessary while the persister is not. The difference from each neighbor is one difference told three ways: Φ is a condition, not a first-order feature; the ground is structural, not brute; and the necessity in play is the necessity of that condition, not of whatever satisfies it.

The result feeds back into the case against the classical sustainer. The conservationist demand is supposed to deliver a being that does the sustaining. Once persistence is grounded structurally, the demand has no work left for such a being to do, and Chapter 6 will close the gap from the other side ([§6.1](<6.1 Greatness.md>)), arguing that a being answering to the classical specification (atemporal, aspatial, immaterial) is ∅ under that description and could sustain nothing even if sustaining were required. The conservation argument needs both halves to stand, and both fail. The fuller engagements with the being the conservationist names are at [§5.2.1](<5.2.1 Divine Simplicity.md>) (the simplicity that is supposed to make it the unconditioned ground), [§5.1.3](<5.1.3 Simultaneous Causation.md>) (the simultaneous causation supposed to make its sustaining concurrent), and [§5.1.1](<5.1.1 Rasmussen's Foundation Argument.md>) (the foundation argument that reasons toward it). The narrower result those depend on is that continued existence does not, by itself, hand the theist the explanandum the argument needs.

*What holds.* The existential-inertia debate is run between a conservationism that grounds persistence in a sustaining God and an inertialism that grounds it in nothing at all. The same move answers both. Persistence is not a transition, so it needs no concurrent actualizer (against the conservationist); but it is not brute either, so the inertialist's default is not the last word (against the strongest inertia critics). Persistence is grounded in Φ, the retention of identity across an interval, which is deeper than any disposition and which does not, by its own necessity, necessitate what it grounds ([§2.8.4](<2.8.4 Necessity Precedes Contingency.md>); L9, [§4.4.9](<4.4.9 Modal Collapse Objection.md>)). The conclusion the inertialist wants is secured (Nature persists without a divine sustainer) on a ground the inertialist cannot supply. The local result is that Φ states the constitutive condition under which persistence counts as persistence and that its necessity does not necessitate any particular persister. Whether a further sustaining explanation is required remains a separate grounding dispute; this section blocks the inference from mere continuation to continuous re-creation but does not settle every conservationist formulation by definition alone.


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