The Leibnizian (Contingency) Cosmological Argument

Leibnizian Contingency Argument

Abstract

Gottfried Wilhelm Leibniz grounds the cosmological argument not in the universe's beginning but in a strengthened Principle of Sufficient Reason: "no fact can be real or existing and no statement true without a sufficient reason for its being so and not otherwise" (Monadology §32). The sufficient reason for the whole "series of things comprehended in the universe of creatures" (§36) "must exist outside this series of contingencies and is found in a necessary being that we call God" (§38) (SEP CA §1). Its medieval ancestors are Ibn Sina's contingency argument and the Third Way of Thomas Aquinas; its contemporary defenders work in modal logic and mereology.

Formal statement

The nine-step SEP reconstruction above states the modern form. Leibniz's own version, per the SEP's natural-theology entry, is distinctive in that it "does not assume or attempt to establish that the world, the collection of all actual contingent beings, has a beginning in time":

Two demands for explanation might still arise: Why is there a world at all rather than none? and: Why does this world exist and not some other world? (SEP NT §3.1)

Neither question, the SEP continues, can be answered by pointing to anything inside the world or inside time. Leibniz's conclusion is that the explanation must lie in a being that is necessary not merely on some hypothesis but absolutely, carrying the ground of its own existence within itself — and that being is God (SEP NT §3.1).

Key evidence / textual basis

Three lines of support are pressed for the load-bearing premises. For premise 2 (the PSR), Richard Taylor's pragmatic defense: the principle "cannot be proved… it is hard to see how one could even make an argument for it without already assuming it"; Alexander Pruss adds that abandoning it "would undercut the practice of science" (SEP CA §4.4). For premise 8 (the universe's contingency): if all the contingent things in the universe ceased to exist simultaneously, the universe as their totality would cease to exist — and what can cease to exist is contingent; Koons gives the claim a mereological formulation (SEP CA §4.2). For the theistic identification (step 9), Timothy O'Connor argues the universe cannot itself be the necessary being "since it is mereologically complex," and that the more viable account of the necessary being is "a purposive agent with desires, intentions, and beliefs"; Koons — as are Craig and Sinclair (2009) — is "willing to identify the necessary being as God" (SEP CA §4.1).

Historically, the argument descends from Ibn Sina's contingency argument, "taken up by Thomas Aquinas (1225–74) in his Summa Theologica (I,q.2,a.3)" (SEP CA §1); Aquinas' Third Way concludes to "some being having of itself its own necessity, and not receiving it from another… This all men speak of as God" (Aquinas, Summa I q.2 a.3). Scripturally, the argument's terminus coheres with the aseity of the God of Ex 3:14 (bib) and with Paul's Areopagus claim that in God "we live and move and have our being" (Acts 17:28 (bib)).

Leading proponents

• Gottfried Wilhelm Leibniz — canonical formulator; strengthened PSR in Monadology §§32–38 (texts not in corpus; compiled via SEP).
• Samuel Clarke — advanced "a similar cosmological argument… around the same time" (1705) (SEP NT §3.1); profile pending.
• Alexander Pruss, Robert Koons, Timothy O'Connor — the contemporary defense: Pruss's reassessment of the PSR and his chapter "The Leibnizian Cosmological Argument" (in Craig and Moreland 2009); Koons's mereological "new look"; O'Connor's derivation of divine attributes from necessary being (SEP CA §1; SEP CA §9). Texts await ingestion; William Lane Craig co-edited the volume containing Pruss 2009 and, with Sinclair, endorses identifying the necessary being as God (SEP CA §4.1).

Strongest counter-arguments

The sharpest modern objection is Peter van Inwagen's modal-collapse argument against the PSR itself: let P be the conjunction of all contingent true propositions and suppose S sufficiently explains P. S cannot be contingent (it would then be a conjunct of P and its own sufficient reason), and S cannot be necessary ("from necessary propositions only necessary propositions follow"). So the PSR is false — or, if retained, everything is necessary and contingency vanishes (SEP CA §4.4). Bertrand Russell's blunter denial: the universe "is just there, and that's all" — and the move from contingent parts to a contingent whole commits the Fallacy of Composition (SEP CA §4.2). Kant objects that identifying the necessary being as the most real being covertly relies on the ontological argument (SEP CA §4.5). Hume's Part-9 battery — treated at full strength as the second view below — attacks both the coherence of "necessary existence" and the demand for a cause of the whole. Mackie presses that even a metaphysically (not logically) necessary God is "logically contingent, such that some reason is required for God's own existence" (SEP CA §4.5). A friendly-fire objection: from within Reformed Epistemology, Alvin Plantinga concludes "that this piece of natural theology is ineffective" and unnecessary, "since belief in God can be properly basic" (SEP CA §1) — a divergence from this wiki's default evidentialist framing.

Responses

To van Inwagen, Pruss replies that "sufficient" is ambiguous: a reason can sufficiently explain without being logically sufficient for (entailing) the explanandum. Since God's connection with the world runs through libertarian free agency, "free actions explain but do not entail the existence of particular contingent states" — blocking the collapse of contingency (SEP CA §4.4). To Russell, Swinburne answers that "uniqueness is relative to description… The objection fails to make any crucial distinction between the universe and other objects" (SEP CA §4.2). To the composition charge, defenders argue the universe resembles the non-fallacious case (a wall of bricks is brick), and Koons's mereological version bypasses the issue (SEP CA §4.2). To Kant and Mackie, the modern reply distinguishes logical from metaphysical necessity: the necessary being is "self-sufficient and self-sustaining," so no ontological argument is invoked and no further reason is owed — "a demand for explaining its existence is inappropriate" (SEP CA §4.5). Whether this reply is principled or ad hoc is where the debate remains joined.

Assessment

Assessment: Strong — the argument enjoys a substantial contemporary revival (Pruss, Koons, Gale, O'Connor, Rasmussen per SEP CA §1), but carries two open liabilities: the PSR's threat of modal collapse, and the gap between "necessary being" and God — per SEP, "every thesis and argument we have considered… is seriously contested" (SEP CA §9).

Humean-Cleanthes Critique

Abstract

In Part 9 of the Dialogues Concerning Natural Religion, David Hume has Demea state the Leibniz-Clarke argument "a priori" — and then, unusually, gives the rebuttal not to the sceptic Philo but to the theist Cleanthes, signalling that Hume took the objections to be decisive even for the religiously committed. The critique's prongs: no matter of fact is demonstrable a priori; "necessary existence" is meaningless or, if meaningful, applies as well to matter as to God; and an eternal causal series needs no cause beyond the causes of its members.

Formal statement

Reconstructed from Cleanthes' speeches: 1. "Nothing is demonstrable, unless the contrary implies a contradiction… Whatever we conceive as existent, we can also conceive as non-existent. There is no being, therefore, whose non-existence implies a contradiction. Consequently there is no being, whose existence is demonstrable" (Hume, Dialogues Part 9). 2. "The words, therefore, necessary existence, have no meaning; or, which is the same thing, none that is consistent" (Hume, Dialogues Part 9). 3. Even granting the notion, "why may not the material universe be the necessarily existent Being, according to this pretended explication of necessity?" (Hume, Dialogues Part 9). 4. "In tracing an eternal succession of objects, it seems absurd to inquire for a general cause or first author" (Hume, Dialogues Part 9). 5. Given causes of each part, no cause of the whole is needed. 6. Therefore, the a priori argument fails at every joint.

Key evidence / textual basis

Demea's target statement is the eighteenth century's clearest précis of the contingency argument: "Whatever exists must have a cause or reason of its existence… we must… have recourse to a necessarily existent Being, who carries the REASON of his existence in himself" (Hume, Dialogues Part 9). Cleanthes' parity move against Clarke is the critique's sharpest edge: Clarke had argued matter cannot be necessary because "any particle of matter may be conceived to be annihilated"; Cleanthes replies that "the same argument extends equally to the Deity… It must be some unknown, inconceivable qualities, which can make his non-existence appear impossible… And no reason can be assigned, why these qualities may not belong to matter" (Hume, Dialogues Part 9). The whole-parts objection follows: "Did I show you the particular causes of each individual in a collection of twenty particles of matter, I should think it very unreasonable, should you afterwards ask me, what was the cause of the whole twenty" (Hume, Dialogues Part 9). Philo adds a sociological coda: the a priori argument convinces only "people of a metaphysical head" (Hume, Dialogues Part 9).

Leading proponents

• David Hume — Dialogues Concerning Natural Religion (1779), Part 9, in corpus in full.
• Contemporary heirs named by SEP — Russell, Mackie (1982), Graham Oppy (2006), Martin, Morriston, Rundle — who "reason that no current version of the cosmological argument is sound or provides probabilistic evidence" (SEP CA §1). Their texts await ingestion; this view is grounded in Hume directly because his text is in-corpus, not because he is the only live critic.

Strongest counter-arguments

Against prong 1: "someone who fails to understand a necessarily true proposition might conceive of it being false, but from this it does not follow that it possibly is false… Hume, it seems, confuses epistemic with ontological conditions" (SEP CA §4.4). Against prongs 1–2, defenders reply that the argument requires only metaphysical, not logical, necessity — a being that "neither came into existence nor can cease to exist" (SEP CA §4.5). Against prong 4, "it seems quite possible to conceive of a non-temporal causal relation… [and] we can coherently conceive of a relation of simultaneous causation" (SEP NT §3.1). Against prong 5, Rowe's classic reply to the "Hume-Edwards principle": "it is one thing for there to be an explanation of the existence of each dependent being and quite another thing for there to be an explanation of why there are dependent beings at all" (SEP CA §4.3). And even granting each member explained, "one still has not answered the two questions mentioned earlier: Why is there a world at all rather than none? and: Why does this world exist and not some other world?" (SEP NT §3.1).

Responses

Hume's defenders press back at each point. On conceivability: the burden lies with whoever asserts a metaphysical impossibility of non-existence. On the necessary-matter parity: the theist's appeal to "unknown, inconceivable qualities" grounding divine necessity is, by Cleanthes' own argument, equally available to the naturalist about matter. On the whole-parts question: whether the collection of all contingent beings is a genuine entity requiring its own explanation, or an "arbitrary act of the mind" (Hume, Dialogues Part 9), is exactly what remains in dispute; Mackie's version insists "we have no right to assume that the universe complies with our intellectual preferences for causal order" (SEP CA §4.4).

Assessment

Assessment: Live — none of Hume's prongs is uncontested, but the parity objection ("why may not the material universe be the necessarily existent Being?") has never been decisively answered without importing further metaphysics; it is the standing challenge any contingency argument must meet.

Spinozist Necessitarianism

Abstract

Baruch Spinoza represents the road not taken within rationalism: accept a PSR at least as strong as Leibniz's, and conclude not that a transcendent God explains a contingent world, but that nothing is contingent at all. The one substance exists necessarily, everything else is a mode of it, and the distinction between God and Nature collapses: "the eternal and infinite Being, which we call God or Nature, acts by the same necessity as that whereby it exists" (Spinoza, Ethics IV, Preface). Spinoza is thus a standing dilemma for the Leibnizian: a rigorous PSR may deliver necessity, but nothing in the principle dictates that the necessary being be transcendent, personal, or free.

Formal statement

1. "Of everything whatsoever a cause or reason must be assigned, either for its existence, or for its non-existence" (Spinoza, Ethics I, Prop. 11, second proof) — Spinoza's PSR.
2. "God, or substance, consisting of infinite attributes… necessarily exists" (Spinoza, Ethics I, Prop. 11).
3. "Besides God no substance can be granted or conceived" (Spinoza, Ethics I, Prop. 14).
4. "Whatsoever is, is in God, and without God nothing can be, or be conceived" (Spinoza, Ethics I, Prop. 15).
5. "Nothing in the universe is contingent, but all things are conditioned to exist and operate in a particular manner by the necessity of the divine nature" (Spinoza, Ethics I, Prop. 29).
6. Therefore, "Things could not have been brought into being by God in any manner or in any order different from that which has in fact obtained" (Spinoza, Ethics I, Prop. 33).

Key evidence / textual basis

Spinoza's second proof of Prop. 11 is a pure sufficient-reason argument: since "no cause or reason can be given, which prevents the existence of God, or which destroys his existence, we must certainly conclude that he necessarily does exist" (Spinoza, Ethics I, Prop. 11). But this necessarily existent substance is not the free Creator of theism: "God does not act according to freedom of the will" (Spinoza, Ethics I, Prop. 32, Coroll. I), and contingency itself is demoted to an artifact of ignorance — "a thing can in no respect be called contingent, save in relation to the imperfection of our knowledge" (Spinoza, Ethics I, Prop. 33, Note I). Hume's Philo gestures toward this very position in Part 9 — "so naturally does it afford an inference directly opposite to the religious hypothesis!" (Hume, Dialogues Part 9). A contemporary cousin is Bede Rundle's proposal that indestructible matter/energy is the necessary being (SEP CA §4.2) — a possibility Aquinas anticipated when he asked whether necessary beings have their necessity "caused by another, or not" (Aquinas, Summa I q.2 a.3).

Leading proponents

• Baruch Spinoza — Ethics (1677), Part I, in corpus in full.
• Bede Rundle — contemporary matter/energy-necessitarian analogue, per SEP; texts not in corpus (SEP CA §4.2).

Strongest counter-arguments

Three objections are pressed against the necessary-universe option. First, O'Connor argues that the universe cannot be the necessary being "since it is mereologically complex," and elementary particles cannot be necessary beings either, "for their distinguishing distributions are externally caused and hence contingent" (SEP CA §4.1). Second, against Rundle-style matter-necessitarianism: could there not have been more or less matter/energy than there is? And "if the matter/energy nexus constitutes the necessary being, what causally follows from that nexus is itself necessary… which is a disquieting position" (SEP CA §4.2). Third, the modal-intuition cost: Spinoza must affirm that this world, in every detail, could not have been otherwise (Ethics I, Prop. 33) — a conclusion most metaphysicians regard as a reductio, forfeiting the very datum (real contingency) that makes the explanatory question pressing.

Responses

The Spinozist can bite each bullet. Necessitarianism is not refuted by its unpopularity; van Inwagen's argument shows that a full-strength PSR entails it (SEP CA §4.4), so the Leibnizian who keeps the PSR while denying necessitarianism must weaken the principle in ways Spinoza need not. To the mereological-complexity objection: the one substance is not a composite of its modes — the modes are in it (Ethics I, Props. 14–15) — so the inference from complexity to contingency begs the question against substance monism. And the theist's escape route (libertarian divine freedom, per Pruss) purchases contingency at the price of explanations that no longer entail their explananda — which the Spinozist regards as abandoning the PSR in all but name.

Assessment

Assessment: Live — Spinozism remains the most rigorous naturalistic appropriation of the PSR, and defines the dilemma every Leibnizian must resolve: weaken the PSR and lose the proof, or keep it and risk proving Spinoza's God instead of Abraham's.

Swinburne's Inductive Version

Abstract

Richard Swinburne holds that the deductive contingency argument fails — but that a probabilistic cousin succeeds as one strand of a cumulative case. He rejects the PSR because it "leads, as it does in Leibniz, to a being that is logically necessary, and such a being cannot explain the logically contingent" (SEP CA §8). In its place he employs Bayes' Theorem: a complex physical universe is more probable given theism than given no further explanation, so the universe confirms theism.

Formal statement

1. If the cosmological argument were deductively valid, "it would be incoherent to assert that a complex physical universe exists and that God does not exist" — but no such incoherence has been demonstrated (SEP CA §8).
2. A good explanatory hypothesis h satisfies p(e|h & k) > p(e|k), where e is the existence of a complex universe and k background knowledge, and scores well on prior probability — for which simplicity "holds the key" (SEP CA §8).
3. Scientific explanation cannot completely explain the universe, "for there are no physical causes apart from the universe itself and parts thereof" (SEP CA §8).
4. Personal explanation in terms of God is simpler and has explanatory power.
5. Therefore the universe's existence is a correct C-inductive argument for theism — it raises the probability of God's existence, as part of a cumulative P-inductive case (SEP CA §8).

Key evidence / textual basis

Swinburne's own summary: "It is very unlikely that a universe would exist uncaused, but rather more likely that God would exist uncaused. The existence of the universe…can be made comprehensible if we suppose that it is brought about by God" (Swinburne 1979: 131–32, quoted at SEP CA §1). The universe calls for explanation because science cannot say "why there are states of affairs at all or why the fundamental natural laws to which science appeals to explain things hold" (SEP CA §8). Crucially, "God is a logically contingent being, and so could have not-existed" (Swinburne 2004: 79, 148, cited at SEP CA §4.5) — which allows a contingent universe to be explained without the modal collapse that threatens Leibniz.

Leading proponents

• Richard Swinburne — The Existence of God (1979; 2nd ed. 2004); primary texts not in corpus, compiled via SEP's detailed exposition.

Strongest counter-arguments

Michael Martin targets the probability machinery: the prior probability of "a complex universe" is fatally ambiguous, and since a free God can create any world or none, "the complexity of this world does not matter in constructing an inductive argument for God's existence" (SEP CA §8). Second, the SEP's editorial observation: in claiming the universe needs explaining, "it is hard not to see that he invokes some formulation of the PSR" (SEP CA §8) — so Swinburne may not have escaped the deductive argument's liabilities, only softened them. Third, deductive defenders object from the other flank: Swinburne's incoherence test is person-relative, so he "cannot so easily dismiss deductive cosmological arguments" (SEP CA §8). Fourth, Mackie's question recurs against a logically contingent God: why does God exist? (SEP CA §4.5).

Responses

Swinburne's reply to the why-God question is simplicity: explanation legitimately stops where "any attempt to go beyond the factors which we have would result in no gain of explanatory power or prior probability" (Swinburne 2004: 89, quoted at SEP CA §8). To Martin, the Swinburnian answers that theism needs no sharp priors over universes, only that an ordered universe is more to be expected on theism — as "a theatre for finite agents to develop and make of it what they will" (Swinburne 1979: 131) — than on the hypothesis of no explanation (SEP CA §8). Whether simplicity can bear that much weight is the live question.

Assessment

Assessment: Live — the inductive version claims less than Leibniz and is correspondingly harder to refute; its vulnerability is concentrated in the contested apparatus of prior probability and simplicity.