Why Necessary Foundations Can’t Produce Contingent Worlds

And What This Means for Classical Theism

A central strategy for resisting necessitarianism is to concede that the ultimate explanatory basis of reality is necessary while insisting that its effects may nonetheless be contingent. According to this view, the world’s fundamental structure—laws, grounding facts, divine nature, metaphysical base, or total causal state—is fixed necessarily, even though what flows from that base could have been otherwise. This position is attractive because it appears to preserve both explanatory depth and modal openness: necessity at the foundation, contingency in the superstructure.

The aim of this essay is to show that this combination is not stable. Once explanation is taken seriously—once it is understood as answering the contrastive question why this rather than otherwise?—the idea that a necessary cause yields a contingent effect collapses. The collapse is not intuitive but structural. Either the effect turns out to be necessary after all, or contingency reappears in the explanatory base, or explanation gives out in brute arbitrariness. In every case, the original promise of the view is lost.

The explanatory demand

Begin with a minimal and widely shared commitment: contingent facts demand explanation. If something could have been otherwise, then there is a salient question as to why it is this way rather than another. This is not an optional metaphysical taste but a built-in feature of contingency itself. To say that a fact is contingent is precisely to say that alternatives were genuinely possible; those alternatives therefore form a contrast class against which explanation is demanded.

Now consider an explanation in the strong sense relevant here—one that is meant to settle the contrast, not merely correlate with the outcome. To explain why E occurred rather than ¬E is to cite something that rules out the alternative. An “explanation” that leaves the contrast open has not done the explanatory work it purports to do.

This contrastive conception of explanation is not an extra assumption layered onto the argument; it is simply what it is to explain a contingent fact at all. Without contrast-resolution, explanation degenerates into description plus shrug.

The necessary-to-contingent proposal

With this in mind, consider the target position. Let G be a necessary ground—necessary laws, necessary total causal state, necessary metaphysical base. Let E be an effect that is claimed to be contingent. The proposal is that G explains E, even though E could have failed to obtain while G remained exactly as it is.

This entails that G is compatible with not-E. There is a genuine alternative, E′ (at minimum, ¬E), that G does not rule out.

At this point, the explanatory question immediately arises:

Why does G yield E rather than E′, given that G itself does not settle between them?

If G is truly the explanation of E, this question must have an answer. And whatever answers it must be something that differentiates E from E′—a difference-maker. Call it D.

So the structure of the explanation becomes:

• G + D ⇒ E

• G + ¬D ⇒ E′ (or at least, G alone does not secure E)

The crucial issue is the modal status of D.

The trilemma

Once D is introduced, the view faces a trilemma.

Case 1: D is necessary

If D is necessary, then the conjunction G ∧ D is also necessary. But if G ∧ D genuinely explains E—that is, if it rules out the relevant alternatives—then E cannot remain contingent. A necessary explanans that settles the contrast produces a necessary explanandum.

So in this case, the original claim that E is contingent collapses. The view slides into full necessitarianism.

Case 2: D is contingent

If D is contingent, then contingency has not been avoided but merely relocated. The real reason E could have been otherwise is that D could have been otherwise. But then the total explanatory basis of E—namely G ∧ D—is not necessary after all.

This undermines the core motivation for the view, which was to combine a necessary foundation with contingent outcomes. Contingency has re-entered the base. The view is no longer a genuine alternative to universal contingency; it is simply contingency with an extra necessary ornament attached.

Case 3: D is brute or unexplained

Finally, the proponent may say that there is no further explanation of why D rather than ¬D obtains. At that point, explanation halts exactly where it is most needed: at the point of selection between genuine alternatives.

But this is precisely the explanatory failure the necessitarian argument diagnoses. To stop here is not to explain why E occurred rather than E′, but to declare that the difference is inexplicable. The contingency remains brute.

Thus the necessary-to-contingent view achieves its result only by abandoning the very explanatory norm that motivated it.

Why probabilistic and indeterministic variants do not help

A common attempt to evade this trilemma appeals to probabilistic explanation. The necessary ground, it is said, fixes only a probability distribution; the actual outcome is contingent.

But probabilistic explanation does not eliminate the selection problem—it merely redescribes it. Even if G necessitates a distribution, the question remains: why did this outcome occur rather than another compatible with the same distribution? The probability measure does not answer that question. Something must still select the actual outcome. That something is again a D, and the trilemma returns unchanged.

The same applies to indeterministic laws, agent causation, or irreducible chance. Either the choice, chance event, or indeterministic transition is itself necessary (in which case the outcome is necessary), or it is contingent (in which case contingency infects the base), or it is brute (in which case explanation fails).

Indeterminism shifts the locus of contingency; it does not dissolve it.

The illusion of denying transmission

At this point, defenders of the view often deny what might be called the “transmission principle”: the claim that a necessary explanans yields a necessary explanandum. But denying transmission does not rescue explanation; it hollows it out.

If a purported explanation leaves open incompatible outcomes without any further difference-maker, then it does not answer the question why this rather than otherwise. It may describe background conditions under which the outcome occurred, but it does not explain why that outcome occurred. Explanation becomes non-contrastive and therefore non-resolving.

In other words, rejecting transmission amounts to rejecting the contrastive character of explanation. And once that is rejected, the claim that G explains E no longer does the work the view needs it to do.

The deeper asymmetry

This exposes a deeper asymmetry between contingency and necessity under explanatory pressure.

Contingent effects demand contrastive explanation. Any explanation that fails to rule out the alternatives inherits that demand. As a result, contingency is upward-infectious: if a contingent fact is explained at all, it must ultimately be explained by something contingent, unless explanation terminates in brute arbitrariness.

Necessity behaves differently. A necessary explanans that genuinely explains—i.e., that settles the contrast—transmits necessity downward without generating new explanatory burdens. No “why otherwise?” question arises, because no alternative was possible.

This is the asymmetry that makes mixed systems unstable. Contingency spreads explanatory debt; necessity discharges it.

Conclusion

The idea that a necessary cause can yield a contingent effect promises the best of both worlds: explanatory depth without modal collapse. But that promise cannot be kept. Once explanation is understood as answering the contrastive question that contingency generates, the view disintegrates.

Either the effect is necessary after all, or contingency reappears in the explanatory base, or explanation stops arbitrarily. There is no fourth option.

The upshot is not that necessitarianism has been proven true, but that it emerges as the only position that treats explanation consistently. The necessary-to-contingent view, by contrast, survives only by quietly weakening explanation at the very point where it is supposed to do its most important work.

That is not a stable resting place.

Appendix

This appendix applies the instability argument to a prominent theological framework. Readers interested only in the general metaphysical thesis may skip it without loss.

The classical theist response

Classical theists—especially in the Thomistic tradition—do not accept the framing that drives the instability argument without qualification. Their reply is sophisticated and deserves to be stated in its strongest form.

1. God as necessary, simple, timeless unity

Classical theists insist that God is not merely necessary, but absolutely simple:

• no parts

• no real distinctions

• no accidents

• no temporal stages

• no unrealized potentials

God’s essence is identical with God’s existence, intellect, and will. There is therefore one eternal divine act, not a sequence of decisions or selections.

This already blocks a crude version of the instability argument: there is no contingent differentiator in God. No “D” can be located in the divine nature.

2. Extrinsic contingency

The key classical move is to locate contingency entirely in the effects, not in God.

God’s willing is necessary as an act, but its terminus—the creature or world—is contingent. The difference between “God exists alone” and “God exists with creation” is said to be an extrinsic denomination of God, not a real difference in God himself.

On this view:

• God is exactly the same whether or not creation exists.

• The contingency lies in the creature’s dependence, not in the divine source.

3. Freedom without deliberation

Classical theists further deny that divine freedom involves:

• deliberation

• weighing alternatives

• choosing among possibilities

God’s freedom is not libertarian but non-necessitated self-expression. God freely wills this world, but not by first confronting open alternatives. Hence, the selection problem is said not to arise.

This is the classical response in its strongest form.

Why this response does not resolve the instability

The problem with the classical reply is not that it introduces contingency into God. It is that it fails to resolve the contrastive explanatory demand at the level of total reality.

1. The contrast persists, even if God does not vary

Consider the following genuine alternatives:

• (A) God exists alone.

• (B) God exists + world W.

• (C) God exists + world W′.

Classical theists insist that God is identical across all three. Grant that. The explanandum, however, is not God, but the total state of reality. And the contrastive question remains:

Why does reality include this effect rather than another (or none), given that the total explanatory source is identical?

Appealing to extrinsic denomination does not answer this question. It redescribes the phenomenon—the difference is “in the effect”—but does not explain why that effect exists rather than another.

2. “No difference-maker” is not an explanation

Classical theists often respond: there is no further fact. God freely wills this world, full stop.

But this lands squarely on the third horn of the original trilemma:

• The difference between outcomes is real.

• The explanans is the same.

• There is nothing that explains the difference.

That is not a deep explanation; it is a principled refusal of explanation. It treats the decisive modal fact—this world rather than another—as brute.

From the standpoint of the explanatory norm that motivated the appeal to God in the first place, this is a failure.

3. Freedom without explanation is explanatory defeat

If divine freedom means:

• God could have done otherwise,

• and there is no reason why God did not,

then the appeal to God no longer improves our explanatory situation. The contingency has simply been pushed back to the divine will and insulated from scrutiny. (I call this a modal firewall. They’re everywhere.)

This is precisely the structure criticized by rationalists from Leibniz onward: a necessary God whose choices are contingent without reason cannot be the ultimate explanation of reality.

The only stable classical option: necessitarian-friendly theism

Once the classical theist accepts the force of the explanatory demand, the available options narrow dramatically. The instability can be avoided only by rejecting the mixed modal picture altogether.

1. The decisive thesis

Given God’s nature, exactly one total reality is possible.

God’s nature does not merely underwrite existence; it fully determines what exists. There are no alternative worlds compatible with the divine essence.

This does not mean:

• God is externally constrained,

• God is caused,

• God lacks sovereignty.

It means:

• God’s nature is internally sufficient to determine God’s act,

• and God’s act is identical with God’s nature.

This is necessity from within, not compulsion from without.

2. Creation as necessary expression

On this view:

• Creation is not a contingent add-on to God.

• It is the necessary expression of divine being.

There is no moment—temporal or logical—at which God could have refrained from creating or created otherwise. Such “alternatives” are not unrealized possibilities; they are impossibilities.

3. Freedom reconceived

Divine freedom is preserved, but reconceived:

God is free because God acts from nothing but God’s own nature.

Freedom does not require alternatives; it requires self-determination. This conception aligns with the rationalist tradition running through Spinoza and Leibniz, and it is already latent in classical doctrines of simplicity and pure act.

What is abandoned is not freedom, but libertarian contingency.

4. Contingency relocated (but not eliminated)

This view allows for:

• internal, relative, or conditional contingency within the world,

• counterfactual dependence among creatures,

• ordinary modal discourse for finite agents.

What it denies is global contingency—contingency at the level of why this total reality exists rather than another.

That is exactly the level targeted by the instability argument.

The final dialectical result

The original instability argument showed that:

• Necessary cause + contingent effect
  ⇒ unresolved selection problem
  ⇒ either contingency at the base or brute fact.

Classical theism avoids locating contingency in God, but it does not avoid locating brute contingency in reality—unless it abandons the claim that God could have done otherwise.

Once that abandonment is made, the position stabilizes.

The upshot

If one is a classical theist and takes explanation seriously, necessitarianism is not optional—it is required.

Anything short of that is a principled stopping-point masquerading as an explanation.

The Strange Loop at the Heart of Necessity: A weird feature of the claim that everything is necessary

Aquinas and the Modal Firewall