The modal-collapse objection holds that a necessary ground generates necessary outputs: an argument that makes the structural conditions of reality inescapable thereby makes everything that happens within them inescapable too. Spinoza reached this conclusion by tracing out the consequences of substance monism, and drew it as a triumph: every mode follows with the force of geometrical demonstration, and the appearance of contingency is a mark of ignorance. Most of his successors reached the same conclusion and tried to find a way to block it. The present account, the objector presses, appears to rebuild the same trap from a different direction: with T, S, and Φ (the three structural conditions the book's argument derives, borne by Time, Space, and Substance) in the place of *Deus sive Natura* (Spinoza's identification: "God or Nature") and the history of the world in the place of the modes.

The modal-collapse objection has a long lineage. Spinoza (*Ethics* -(Spinoza, B., (1677) 1996)) drew it as a positive conclusion: substance is necessary, its modes follow with geometrical necessity, and contingency is an illusion of perspective. Leibniz (*Theodicy* -(G. W. Leibniz, 1710)) reached a softer form: God necessarily chooses the *best possible world*, and the specific history of this world is therefore fixed with a necessity one step removed from Spinoza's. Modern defenses: Pruss (*The Principle of Sufficient Reason* -(Pruss, Alexander R., 2006)) presses the Leibnizian version against necessitarian accounts of grounding. Van Inwagen (*An Essay on Free Will* -(Peter van Inwagen, 1983)) sharpens the deterministic relative, the Consequence Argument: if the laws and the past are necessary, the future is necessary too. Rasmussen (*How Reason Can Lead to God* -(Rasmussen, Joshua, 2019)) applies the modal-collapse worry to necessitarian alternatives to classical theism. Against the collapse, the contemporary literature runs thick: Plantinga (*The Nature of Necessity* -(Plantinga, A., 1974)) deploys the de dicto/de re distinction in ways that block various propagation moves; Swinburne (*The Christian God* -(Richard Swinburne, 1994)) defends a libertarian space within theism; the open theists (Hasker, Sanders) reject the collapse by denying the necessity of the antecedents. The contemporary grounding literature establishes the framework the present reply uses. Fine ("Guide to Ground," -(Fine, Kit, 2012)) and Rosen ("Metaphysical Dependence: Grounding and Reduction," -(Rosen, Gideon, 2010)) set out grounding as a relation of constitutive determination and defend the principle that a full ground necessitates what it grounds; Schaffer (*On What Grounds What* -(Schaffer, Jonathan, 2009); *Monism* -(Schaffer, Jonathan, 2010)) and Dasgupta -(Shamik Dasgupta, 2014) develop the apparatus the present reply turns on: above all the distinction, owed to Fine, between full and partial ground. The structural account sits closest to Dasgupta's line on grounding and adds: the specific grounds at issue are T, S, and Φ, and their necessity is compatible with the contingency of what they ground because they are only a partial, structural ground of any particular change, never its full ground.

The objection bears on two of the argument's central theses. The Modal Identity is established at [§2.6.6](<2.6.6 Modal Identity.md>): the necessity of the structural conditions (□(T∧S∧Φ)) entails □◇C, the necessary *possibility* of change, not □C, the necessity of change itself. The Necessity of Nature is then established at [§2.8.5](<2.8.5 Necessity of Nature.md>): the specific character of the natural order is constrained by, but not reducible to, the structural conditions. If the modal-collapse objection succeeds, one of two things goes wrong: either the distinction between □◇C and □C dissolves (collapsing the stage into the play), or the grounding relation between structure and specifics is productive (collapsing the contingent specifics into the necessary structure). Both collapses entail Spinozism. The argument would have generated, by a different line, the very view Hume thought Spinoza's necessitarianism reduced to absurdity.

A clarification before the moves. The objection is not that contingency is difficult to square with the argument: it is that contingency is incompatible with it. Three forms of the move press that incompatibility at three resolutions: the deterministic version, the Leibnizian best-of-all-worlds version, and the Spinozan propagation version. The space they cover is the space in which modal collapse could be forced. Each misreads what the argument establishes and misreads what grounding does.

*First.* The van-Inwagen-style propagation move presses the deterministic version. Necessary laws plus necessary initial conditions yield necessary outcomes. If T, S, and Φ are necessary, and the laws of physics follow from the structural roles, the laws are necessary too. Necessary laws plus a fixed past fix the future, so every event is necessary. The Consequence Argument delivers the collapse.

The Modal Identity of [§2.6.6](<2.6.6 Modal Identity.md>) draws a line the objection ignores. What the argument establishes is □◇C (the *possibility* of change is necessary), not □C (change occurs necessarily). Structural necessity fixes what is structurally possible, not which possibilities are actualized. A necessary stage does not script the contingent play. The necessity of T, S, and Φ constrains the *type* of physical law (any law must be expressible as a structural relation among the roles), but it does not fix the specific content. Which symmetry groups govern, which constants obtain, which particles compose the physical domain: these are contingent facts within the necessary architecture. Quantum theory supplies interpretations on which token history is genuinely open, but deterministic interpretations remain live. The modal-collapse reply does not depend on settling that dispute: the structural roles do not by themselves fix laws, initial conditions, or outcomes, so modal collapse does not follow from their necessity alone. The Consequence Argument targets determinism. The present account is not committed to determinism.

*Second.* The Leibnizian best-possible-world version goes deeper. A necessary, perfectly good ground must produce the best possible outcome. If the structure is necessary and it generates a universe, that universe must be the best possible one. Anything less contradicts the ground's perfection. So the specific universe is necessary after all. Modal collapse returns through the back door.

The Leibnizian move presupposes a necessary evaluative subject: something that ranks possible universes and selects the best. The present account posits no such subject. T, S, and Φ are structural roles, not agents. They permit contingency; they do not rank it. The Leibnizian version gets traction against classical theism, where a necessary perfect Being must choose the best; it loses traction against a structural account with no such Being to rank outcomes. An impersonal version of the same demand fares no better. Axiarchism (Leslie, *Value and Existence* -(Leslie, John, 1979)) drops the chooser and grounds the demand in value itself: the good, on this view, tends toward its own actuality with no one selecting it. But a value that actualizes itself still actualizes some determinate configuration rather than the field of alternatives it leaves unactualized, and picking one over the rest is exactly the ranking operation the reply above blocks, run without an agent to perform it; value monism inherits the subject's job without inheriting a subject to do it. Structure permits contingency; it does not rank it, personally or impersonally. Sharper still: the Leibnizian objection, applied to classical theism, generates exactly the collapse the theist wanted to avoid. If the Maximally Great Being is necessarily perfect and necessarily creates the best, the MGB's freedom collapses into predetermined output. The objection is a better argument against classical theism than against the present account.

*Third.* The Spinozan propagation version goes severest. Necessity propagates through grounding relations. If the ground is necessary and the relation is grounding, the grounded is necessary. A necessary structural base cannot ground contingent content, because grounding transmits modal status. The argument has smuggled in contingency it has no right to.

> [!lemma]
> **Constitutive Grounding Non-Propagation** · **L9** · *Lemma toward Modal Collapse Resistance*
>
> Two relations must be kept apart. □(T∧S∧Φ) and □◇C are not ground and grounded but one fact under two readings: by the Modal Identity, the necessity of the structural conditions just is the necessary possibility of change read modally, so □◇C carries its necessity by identity, not by transmission across a grounding relation. The structural conditions also ground the particular changes, but only in part: to be a change at all is to instantiate T, S, and Φ, so the roles enter every change as a necessary structural constituent, while what makes a given change occur rather than another, its initial conditions, its open quantum outcome ([§7.7](<7.7 Cosmic History.md>)), lies outside them. The necessity of the conditions is compatible with the contingency of what is conditioned. □(T∧S∧Φ) ⊢ □◇C, not □C. (Modal Identity: [§2.6.6](<2.6.6 Modal Identity.md>))

Spinozan propagation holds only if T, S, and Φ are the *full* ground of each particular change: only if fixing the structural conditions fixes which changes occur. They are not. The roles ground the *possibility* of change and enter each actual change as a necessary structural constituent, but they are never the whole of what grounds a given change: which change occurs turns on contingent specifics (initial conditions, the open quantum outcome of [§7.7](<7.7 Cosmic History.md>)) that the roles leave undetermined. Grant even the strongest grounding-necessitarian principle, that a full ground necessitates what it grounds; a merely partial ground does not, and T, S, and Φ are at most a partial, structural ground of any particular change. That T, S, and Φ are necessary entails any actual change instantiates them; it does not entail any particular change had to occur.

A kindred move presses through mereology. Schaffer's -(Schaffer, Jonathan, 2010) priority monism holds that the cosmos is the fundamental object and all its parts derive from it by ontological grounding. If grounding transmits necessity, every part is necessary. The reply is the same in mereological vocabulary. Priority monism by itself does not decide whether the cosmos fully or only partly grounds each configuration of its parts. Blocking collapse requires the additional thesis that the necessary structural base underdetermines those configurations; it cannot be read off monism alone. Priority monism does not generate modal collapse once the partial/full ground distinction is drawn.

The Lewisian plurality, which proposes a different reduction of modality, is [§4.4.1](<4.4.1 Modal Realism.md>). Williamson's necessitism, which gives the necessity claim its formal vocabulary, is [§4.4.6](<4.4.6 Necessitism.md>). Sider's structuralism, which deflates the necessity claim rather than embracing it, is [§4.4.7](<4.4.7 Sider's Structuralism.md>). The Whiteheadian process alternative, which relocates Substance into verb form, is [§4.4.8](<4.4.8 Whiteheadian Process Metaphysics.md>). The simultaneous-causation response, which grounds an atemporal production of the world, is [§5.1.3](<5.1.3 Simultaneous Causation.md>).

*What converges.* Each of the three forms misreads what the argument establishes and what grounding does. The Consequence Argument targets determinism, which the present account is not committed to: □◇C fixes what is structurally possible, not which possibilities are actualized, and the structural roles do not by themselves fix laws, initial conditions, or outcomes, whichever quantum interpretation obtains. The Leibnizian best-world version presupposes a necessary evaluative subject the present account does not posit, and is, in fact, a sharper argument against classical theism than against the present account. Spinozan propagation holds only if T, S, and Φ fully ground each particular change rather than partly. The roles ground the possibility of change and enter each actual change as a necessary constituent, but the contingent specifics that fix which change occurs lie outside them, so a merely partial ground does not propagate modal status in the Spinozan sense.

Spinoza wrote the *Ethics* *more geometrico* (Latin: "in the geometrical manner", his method of presenting metaphysics in the form of definitions, axioms, and propositions). The necessitarian conclusion he reached (God is nature, nature is necessary, every mode follows with the force of geometrical demonstration) has haunted rationalist metaphysics ever since. Most of his successors tried to restore contingency by loosening the grounding relation between substance and mode. The structural account restores it by a different line: by clarifying what was grounded in the first place. T, S, and Φ ground the *possibility* of change, not the necessity of any particular change. The stage may be necessary without the argument thereby making every detail of the play necessary. Spinoza saw what happens if the necessary base fully grounds its modes, so that necessity transmits unrestricted; he saw correctly. The mistake was not in following the logic. It was in assuming the base must be the full ground of what follows from it.

Necessity at the base permits contingency at the leaves.


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← [4.4.8 Whiteheadian Process Metaphysics](<4.4.8 Whiteheadian Process Metaphysics.md>) | [4.4.10 Gasking's Parody of the Ontological Argument](<4.4.10 Gasking's Parody of the Ontological Argument.md>) →
