Notes · Religious StudiesUK · A-Levels

Arguments for the existence of God

The classical arguments for God's existence fall into two families: the a posteriori design and cosmological arguments, which reason from features of the world to a designer or first cause, and the a priori ontological argument, which claims God's existence follows from the concept of God alone. This topic reconstructs each argument as a set of premises and a conclusion, tests its validity and soundness, and weighs the major objections of Hume, Kant, Gaunilo and others against the defences offered in reply.

5 sections~25 min reading time2 competenciesLevel Foundation 1 · Standard 2 · Advanced 2

T·0111 / 16

Exam profile

AO1 · Demonstrate knowledge and understanding of the design, cosmological and ontological arguments, their key thinkers and technical vocabularyAO2 · Analyse the logical form of each argument and evaluate its success against the principal criticisms, reaching a justified judgement

Operators:explainanalyseassessevaluate'...' Discussto what extent

basic level

At AS-Level, expound each argument accurately with its named proponents and give the leading objection to each.

higher level

At full A-Level, reconstruct each argument premise by premise, distinguish validity from soundness, sustain the dialectic of objection and reply, and judge whether the arguments succeed singly or only as a cumulative case.

Depth

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Contents · 5 sections

Arguments for the existence of God

The taxonomy of arguments: a priori and a posteriori#

FoundationAQA 7062/1 Section A: Arguments for the existence of GodDfE GCE Religious Studies subject content

Classifying the arguments for God

Fig. 1The ontological argument alone is a priori; the design and cosmological arguments reason a posteriori from features of the world.

Before any argument for God can be assessed it must be classified, because its type dictates what would count as a good objection. An a priori argument is one whose premises and conclusion can be known independently of sense experience, by reason and reflection on concepts alone; the ontological argument is the only a priori argument for God, claiming that the very concept of God entails his existence. An a posteriori argument, by contrast, reasons from premises drawn from observation and experience of the world; the design (teleological) and cosmological arguments are both a posteriori, beginning from features we observe — order, purpose, motion, causation, contingency — and inferring God as their explanation. The distinction matters because an a priori argument can, if valid and its premises true, deliver a necessary conclusion, whereas an a posteriori argument's conclusion is only ever as secure as our reading of the empirical evidence.

A second distinction cuts across the first: whether an argument is deductive or inductive. In a deductive argument the conclusion follows necessarily from the premises, so that if the premises are true the conclusion cannot be false; the argument is then valid, and a valid argument with true premises is sound. Anselm's ontological argument and (arguably) Aquinas' cosmological Ways are framed deductively. In an inductive argument the premises make the conclusion probable but not certain; the conclusion goes beyond the evidence, so even true premises leave room for doubt. Paley's design argument and Swinburne's cumulative case are inductive: they claim God is the best or most probable explanation of the data, not a logically guaranteed one. A candidate who confuses the two will misjudge an argument — demanding deductive certainty from an argument that only claims probability, or vice versa.

A third pairing, analytic and synthetic, underlies the ontological debate in particular. An analytic statement is true or false in virtue of the meanings of its terms ('a bachelor is unmarried'); a synthetic statement's truth depends on how the world actually is ('the door is open'). Anselm treats 'God exists' as, in effect, analytic — existence is contained in the concept of the greatest conceivable being — whereas Kant's decisive objection is that 'exists' is not a predicate that can be built into a concept, so that 'God exists' must be synthetic and cannot be settled by analysing the idea of God. Holding these three distinctions steady (a priori/a posteriori, deductive/inductive, analytic/synthetic) is the discipline that keeps an evaluation precise rather than impressionistic.

Finally, the arguments can be read either individually or cumulatively. Read individually, each argument stands or falls on its own; a single fatal objection sinks it. Read cumulatively, as Richard Swinburne proposes, no single argument is decisive but each raises the probability of theism, and together they make God's existence more probable than not, in the way that several independent strands of circumstantial evidence can jointly convict where no strand alone would. This framing is important for evaluation because an argument that fails as a proof may still succeed as a probabilistic consideration, and a fair judgement must say which standard it is applying.

Worked example

Classifying and evaluating standards

A student says 'the ontological argument is weaker than the cosmological argument because it does not use any evidence.' Assess this claim.

Identify the types
The ontological argument is a priori and deductive; the cosmological argument is a posteriori. Using no empirical evidence is a feature of the a priori method, not a defect.
Name the appropriate standard
A deductive a priori argument should be judged on validity and the truth of its conceptual premises; an a posteriori argument on how well it explains the evidence.
Expose the error
The claim measures an a priori argument by an a posteriori standard (evidence). If sound, an a priori argument would actually be stronger, delivering a necessary rather than a probable conclusion.
Give the fair criticism
The real weakness of the ontological argument is not its lack of evidence but Kant's objection that existence is not a predicate — a criticism internal to its own method.

Result: The student's reasoning is confused: it faults the ontological argument for being a priori. The cogent objection to it is Kant's, not the absence of evidence; each argument must be judged by the standard proper to its type.

Typical mistakes

Muddling a priori and a posteriori — e.g. calling the design argument a priori because it concludes to God; the test is the source of the premises, not the conclusion.
Treating 'valid' and 'true' as the same: an argument can be valid yet unsound (false premise), and can reach a true conclusion by an invalid route.

Active revision

Explain the difference between a priori and a posteriori arguments for the existence of God, using the ontological and cosmological arguments as examples. (Structured AO1 response)

Active recall

Recall the key points — then reveal.

Sources: GCE AS and A level subject content for religious studies (Department for Education)

The teleological (design) argument#

StandardAQA 7062/1 Section A: Arguments for the existence of GodDfE GCE Religious Studies subject content

Paley's design argument by analogy

Fig. 2The argument moves from the design of a human artefact (the watch) to the design of the natural world, and thence to a cosmic designer.

The teleological argument (from the Greek telos, 'end' or 'purpose') reasons from apparent order, regularity and purpose in the universe to a designing intelligence. Aquinas' Fifth Way, in the Summa Theologica, is its classic scholastic form: he observes that natural bodies which lack knowledge — such as the parts of the physical world — nevertheless act towards an end, achieving their goal not by chance but regularly and for the best; but a thing that lacks awareness can only tend towards an end if it is directed by something that does have awareness, as an arrow is directed by an archer; therefore there exists an intelligent being by whom all natural things are directed to their end, and this being we call God. Aquinas' argument is qualitative and cosmic in scope: it is impressed by the very regularity of nature, not by any particular contrivance.

William Paley, in Natural Theology (1802), gives the argument its most famous form with the watch analogy. If, crossing a heath, I found a stone, I might suppose it had always lain there; but if I found a watch, its intricate parts adjusted and combined to produce regular motion — the spring, the wheels, the hands — I would infer that it had a maker who designed it for a purpose, even if I had never seen a watch made and even if the watch sometimes went wrong. Paley then argues that the natural world exhibits contrivance of exactly this kind, only greater: the human eye, adjusted for vision as a telescope is for sight, is his prime example. The universe is therefore like a vast machine whose parts are fitted to purposes, and so, by analogy, it too must have a designer, whom Paley identifies as God. This is design qua purpose (contrivance), complemented by design qua regularity (the lawful order of the heavens).

F. R. Tennant, in the twentieth century, restated the argument in two fresh ways that sidestep some older objections. His anthropic argument observes that the universe is finely adjusted to permit the emergence of intelligent life: the cosmos is intelligible, obeys mathematical laws, and provides just the conditions in which conscious observers can arise, which he takes to be more probable on theism than on chance. His aesthetic argument notes that humans possess an appreciation of beauty — of music, art and nature — that confers no evolutionary advantage and so is not required for survival, and is better explained as the gift of a designer. These modern versions are explicitly inductive and probabilistic: they claim design is the best explanation, not a certainty.

Reconstructed formally, Paley's argument runs: (P1) the natural world exhibits complex order in which means are adjusted to ends; (P2) such adjustment of means to ends is, in every case whose origin we know (the watch), the product of intelligent design; (P3) like effects have like causes; therefore (C) the order of the natural world is probably the product of an intelligent designer, namely God. The argument is a posteriori and inductive: it moves from observed features to their most probable explanation by analogy, and its strength depends entirely on how good the analogy between natural objects and human artefacts really is — the exact point at which its critics attack.

Worked example

Model evaluation plan: does the design argument succeed?

Plan an essay assessing whether the design argument proves God's existence.

Thesis
The design argument does not prove God, but it survives Hume and Darwin better as an inductive 'best explanation' (Tennant, Swinburne) than as a proof.
Argument (AO1)
Expound Paley's watch analogy and Aquinas' Fifth Way; add Tennant's anthropic fine-tuning as the strongest modern form.
Counter (AO2)
Hume: the analogy is weak (the universe is unique, more like an organism than a machine), the designer need not be the God of theism (could be many, imperfect, or a committee), and the epicurean hypothesis explains order without design. Darwin: natural selection explains biological adaptation without a designer.
Response
Fine-tuning of the cosmic constants is untouched by Darwin (it precedes biology); Swinburne argues theism is the simplest explanation of a law-governed, life-permitting universe.
Judgement
Weigh: as deductive proof it fails (Hume); as inductive support, fine-tuning gives it residual force, but the multiverse rival keeps the verdict short of proof.

Result: A defensible judgement: the design argument is not a proof, but in its fine-tuning form it remains a genuine, if inconclusive, probabilistic consideration in favour of theism.

Typical mistakes

Attributing the watch analogy to Aquinas: it is Paley's. Aquinas' Fifth Way is about unconscious things acting towards ends, not about contrivance.
Presenting the design argument as a deductive proof; it is an argument from analogy to the best/most probable explanation, and treating it as a proof invites easy refutation.

Active revision

'The design argument proves the existence of God.' Analyse the design argument and assess this claim. (Extended essay)

Active recall

Recall the key points — then reveal.

Sources: GCE AS and A level subject content for religious studies (Department for Education)

The cosmological argument#

StandardAQA 7062/1 Section A: Arguments for the existence of GodDfE GCE Religious Studies subject content

Aquinas' Third Way (from contingency)

Fig. 3From the contingency of things and the impossibility that all beings are contingent, Aquinas infers a necessary being.

The cosmological argument reasons a posteriori from the existence of the universe to a first cause or necessary being. Aquinas' first three Ways are its classic forms. The First Way (from motion) observes that things in the world are in motion (change); whatever is moved is moved by another; this cannot regress infinitely, for then there would be no first mover and so no subsequent motion; therefore there is a first, unmoved mover, which we call God. The Second Way (from causation) runs identically for efficient causes: nothing can be the cause of itself, an infinite regress of causes is impossible, so there is a first uncaused cause. Both Ways rest on the rejection of an actual infinite regress and on the claim that the series requires a first term outside itself.

The Third Way (from contingency) is the most philosophically interesting. It observes that things in the world are contingent — they come to be and pass away, so it is possible for them not to exist. Aquinas argues that if everything were contingent, then at some time nothing would have existed (since each contingent thing at some time does not exist); but if there had ever been nothing, nothing could have come into existence, since nothing comes from nothing; so there would be nothing now, which is false. Therefore not everything is contingent: there must exist a being whose existence is necessary — that does not depend on another — and this necessary being is God. The argument is deductive in form and turns on the concept of contingency and the impossibility of an infinite regress of dependent beings.

The Kalam cosmological argument, of Islamic origin and revived by William Lane Craig, is a sharper, temporal version: (P1) whatever begins to exist has a cause; (P2) the universe began to exist; therefore (C) the universe has a cause. Craig defends P2 both philosophically (an actual infinite series of past events is impossible) and scientifically (Big Bang cosmology and the second law of thermodynamics point to a finite past). He then argues that the cause of the universe must be uncaused, timeless, spaceless, immensely powerful and personal — for only a personal agent could bring about a temporal effect from a timeless state. Leibniz gives a further version resting on the principle of sufficient reason: everything must have a reason or explanation; the universe as a whole requires a sufficient reason for its existence, which cannot lie within the contingent series and so must be a necessary being, God.

Hume and Russell press the standard objections. Hume argues that we have no experience of universes being caused, so the causal principle cannot be extended to the cosmos as a whole; that the notion of a 'necessary being' is incoherent, since whatever we can conceive as existing we can conceive as not existing (existence is never logically necessary); and that the 'fallacy of composition' is committed in inferring that because each part of the universe has a cause, the whole has a cause. Russell added that 'the universe is just there, and that's all' — it may be a brute fact requiring no external explanation, so the demand for a sufficient reason simply may not apply to the totality. The theist replies that a law-governed, contingent cosmos cries out for explanation and that arbitrarily exempting the universe from the causal principle is special pleading.

Worked example

Reconstruction and critique of the Kalam argument

Reconstruct the Kalam cosmological argument and assess whether it is sound.

State the argument
P1: whatever begins to exist has a cause. P2: the universe began to exist. C: therefore the universe has a cause. The form is valid (modus ponens-like).
Test P1
P1 is intuitive but rests on causation as we experience it within time; Hume denies we can extend it to the universe's origin, where there is no 'before'.
Test P2
Craig supports P2 by the impossibility of an actual infinite past and by Big Bang cosmology. Critics reply that quantum cosmology may allow an uncaused beginning, or a past-eternal multiverse.
Test the bridge to God
Even granting a cause, the leap to a personal, timeless God is a further inductive step; the cause could be impersonal or naturalistic.
Judgement
The argument is valid; its soundness depends on P2 and on the identification of the cause with God, both of which are contestable, so it establishes at most a probable first cause.

Result: The Kalam argument is valid and its premises are defensible, but it falls short of proof: it supports a first cause more than the specific God of classical theism.

Typical mistakes

Claiming Aquinas argues the universe 'began to exist' — that is the Kalam claim; Aquinas' Ways are about dependency here and now, and he actually thought the universe's beginning was known only by revelation.
Stating the argument as 'everything has a cause, so the universe has a cause, so God has a cause' — this self-defeating version misreads the premise, which exempts the necessary/uncaused being.

Active revision

'The cosmological argument fails because it commits the fallacy of composition.' Assess this view. (Extended essay)

Active recall

Recall the key points — then reveal.

Sources: GCE AS and A level subject content for religious studies (Department for Education)

The ontological argument#

AdvancedAQA 7062/1 Section A: Arguments for the existence of GodDfE GCE Religious Studies subject content

Anselm's Proslogion 2 as a reductio

Fig. 4Supposing God existed only in the mind leads to a contradiction with the definition of God, so God must exist in reality.

The ontological argument, first stated by Anselm of Canterbury in the Proslogion (1078), is the sole a priori argument for God: it claims that God's existence can be deduced from the concept of God alone, without any appeal to experience. Anselm defines God as 'that than which nothing greater can be conceived' (aliquid quo nihil maius cogitari possit). In Proslogion 2 he argues: even the fool who says 'there is no God' (Psalm 14) understands this definition, so God exists at least in the understanding; but a being that exists in reality as well as in the understanding is greater than one that exists in the understanding alone; so if God existed only in the understanding, we could conceive of something greater (the same being existing in reality), which is a contradiction, since God is that than which nothing greater can be conceived; therefore God must exist in reality as well as in the understanding.

In Proslogion 3 Anselm gives a second, stronger form concerning necessary existence: a being that cannot be conceived not to exist is greater than one that can be conceived not to exist; God is that than which nothing greater can be conceived; therefore God cannot be conceived not to exist — God has necessary, not merely contingent, existence. This second version is important because it survives some objections to the first: it treats God's existence not as one more property added to a being but as the special mode of existence (necessity) proper to the greatest conceivable being. Descartes later restated the argument in his Fifth Meditation: God is a supremely perfect being; existence is a perfection; a supremely perfect being that lacked existence would lack a perfection and so not be supremely perfect; therefore God, by definition, exists — just as the concept of a triangle entails that its angles sum to two right angles.

Gaunilo, Anselm's contemporary, gave the first great objection in 'On Behalf of the Fool'. He argues by parody: imagine the most perfect island conceivable; by Anselm's reasoning, since an island that exists is greater than one that does not, the most perfect island must exist — which is absurd. So Anselm's logic must be flawed, for it would conjure any perfect thing into existence merely from its concept. Anselm replied that the argument works only for that than which nothing greater can be conceived — a being with necessary existence — and not for contingent things like islands, which can always be improved and can be conceived not to exist; the reductio does not transfer.

Kant delivered what is widely regarded as the decisive objection: existence is not a predicate. When I say a thing exists I do not add a property to my concept of it; '100 real thalers contain no more than 100 possible thalers' — the concept is the same, existence merely posits that an instance of it obtains. So 'existence' cannot be part of the definition of God in the way 'omnipotence' is; and therefore 'God exists' is a synthetic claim about whether anything answers to the concept, not an analytic truth deducible from the concept. Norman Malcolm defended Proslogion 3 by arguing that necessary existence, unlike existence, may be a legitimate predicate of God, so that God's existence is either impossible or necessary and, since not impossible, necessary. Bertrand Russell's theory of descriptions reinforces Kant: 'exists' is not a first-order predicate of objects but a second-order quantifier ('there is an x such that...'), so the grammar that makes the argument seem to work is misleading.

Worked example

Model evaluation plan: does the ontological argument work?

Plan an essay assessing whether the ontological argument succeeds.

Thesis
The ontological argument fails as a proof because Kant's objection stands, though Malcolm's necessary-existence form is the most resilient version.
Argument (AO1)
Expound Proslogion 2 and 3 and Descartes' perfection version; explain the a priori, analytic claim.
Counter (AO2)
Gaunilo's island; Kant that existence is not a predicate, so 'God exists' is synthetic; Russell's logic of 'exists' as a quantifier.
Response
Anselm answers Gaunilo (islands are contingent); Malcolm answers Kant by arguing necessary existence is a genuine predicate, giving 'God's existence is impossible or necessary; not impossible; so necessary.'
Judgement
Malcolm's move needs the further premise that God is not impossible (coherent), which is precisely what is in dispute; so the argument cannot compel a non-believer, though it may articulate the believer's concept of God.

Result: A justified judgement: the ontological argument does not prove God to the sceptic, since it presupposes the coherence of the concept it aims to instantiate, but Proslogion 3 shows the theist's God is rightly conceived as a necessary being.

Typical mistakes

Treating Gaunilo's island as decisive without giving Anselm's reply (islands are contingent and improvable; the parody does not apply to a necessary being).
Paraphrasing Kant as 'you cannot define things into existence' without explaining the technical claim that existence adds nothing to a concept, which is where the argument's force lies.

Active revision

'Kant's objection that existence is not a predicate destroys the ontological argument.' Discuss. (Extended essay)

Active recall

Recall the key points — then reveal.

Sources: GCE AS and A level subject content for religious studies (Department for Education)

Do the arguments succeed? The cumulative case#

AdvancedAQA 7062/1 Section A: Arguments for the existence of GodDfE GCE Religious Studies subject content

A priori and a posteriori arguments compared

Fig. 5The two families differ in method and objection but share the aim of establishing God and the burden of the problem of evil.

A final judgement must decide by what standard the arguments are being assessed. As deductive proofs intended to compel any rational person, all three arguments arguably fail: the ontological argument presupposes the coherence of its concept (Kant), and the a posteriori arguments underdetermine their conclusion, reaching at most a first cause or a designer rather than the omnipotent, omnibenevolent God of classical theism (Hume). Judged as proofs, the honest verdict is that none is coercive. But this standard may be too demanding: very few substantive philosophical conclusions can be proved with deductive certainty, and to reject theism for failing a test that ethics, other minds and the external world also fail would be inconsistent.

Richard Swinburne therefore recasts the project inductively and cumulatively. No single argument, he grants, is a proof; but each raises the probability of theism, and their combined weight, together with religious experience, makes God's existence more probable than not. He uses the language of confirmation theory: a hypothesis is confirmed by evidence it renders more likely than any rival does, and he argues that theism, being a simple hypothesis (one being of infinite power, knowledge and goodness) that explains the existence of a law-governed, fine-tuned, conscious-life-permitting universe, is the best explanation of the total evidence. On this reading the arguments are strands in a cable rather than links in a chain: even if each strand is individually weak, the cable can bear weight.

Critics resist the cumulative move on two fronts. First, several individually invalid arguments do not necessarily sum to a strong case: zero plus zero is zero, and adding weak analogies together may compound rather than cancel their weaknesses. Swinburne answers that the arguments are not worthless but merely inconclusive individually, and inconclusive evidence can legitimately accumulate, as in a courtroom. Second, the atheist offers a rival cumulative case: the problem of evil, the hiddenness of God, the success of naturalistic explanation, and the sociological explicability of religion together make atheism the better total explanation. Which cumulative case is stronger then turns on contested prior probabilities and on how much weight the problem of evil is allowed to carry.

The considered verdict most defensible at A-Level is nuanced. The arguments do not prove God, and a candidate who claims they do will overreach; but they are not therefore worthless. The cosmological and design arguments, in their contingency and fine-tuning forms, raise real questions that naturalism must also answer, and the ontological argument clarifies the theist's concept of God as a necessary being. Whether the cumulative case tips the balance towards theism depends on how one weighs the countervailing problem of evil — which is why this topic connects directly to the next. A strong essay reaches a judgement, states the standard it is applying, and acknowledges what a reasonable opponent would say.

The arguments also interlock conceptually, which is itself evaluatively significant. The cosmological argument yields a necessary being; the ontological argument analyses what necessary existence means; the design argument supplies the intelligence and purposiveness; and religious experience (the next topics) claims direct acquaintance with the being so described. This coherence is what allows Swinburne to treat them as converging on a single hypothesis rather than as a heap of unrelated proofs, and it is the deepest reason the cumulative case cannot simply be dismissed as adding zeros.

Worked example

Weighing proof against probability

Explain how a candidate can reach a defensible judgement on whether the arguments for God succeed.

Fix the standard
Decide whether success means deductive proof (compels all) or inductive support (raises probability). State it explicitly.
Apply the strict standard
As proofs, all fail: Kant sinks the ontological; Hume shows the a posteriori arguments underdetermine the God of theism.
Apply the modest standard
As probabilistic considerations, the contingency and fine-tuning arguments retain force; Swinburne's cumulative case treats them as converging strands.
Admit the rival case
The atheist's cumulative case (evil, divine hiddenness, naturalism's success) must be weighed against the theistic one.
Judge
Conclude that the arguments do not prove God but keep theism a live rational option, with the balance turning on the problem of evil.

Result: The arguments fail as proofs but succeed as a cumulative probabilistic case only to the extent that the problem of evil does not outweigh them — a judgement that is defensible precisely because it names its standard and its decisive variable.

Typical mistakes

Ending with 'it is a matter of faith/opinion' — this abandons evaluation; examiners reward a weighed judgement even if tentative.
Assessing the arguments only individually and never addressing whether they succeed jointly, missing the cumulative-case debate the specification expects.

Active revision

'The arguments for God's existence are more persuasive taken together than individually.' Evaluate this claim. (Extended essay)

Active recall

Recall the key points — then reveal.

Sources: GCE AS and A level subject content for religious studies (Department for Education)

References & sources

Sources

Department for Education

GCE AS and A level subject content for religious studies

Arguments for the existence of God

5 sections~25 min reading time2 competenciesLevel Foundation 1 · Standard 2 · Advanced 2

Arguments for the existence of God

Key points

Classifying and evaluating standards

Key points

Model evaluation plan: does the design argument succeed?

Key points

Reconstruction and critique of the Kalam argument

Key points

Model evaluation plan: does the ontological argument work?

Key points

Weighing proof against probability

Sources

Arguments for the existence of God

Key points

Classifying and evaluating standards

Key points

Model evaluation plan: does the design argument succeed?

Key points

Reconstruction and critique of the Kalam argument

Key points

Model evaluation plan: does the ontological argument work?

Key points

Weighing proof against probability

Sources