Cosmological Argument

The problem it answers

Why is there something rather than nothing? Why does the world exist at all, and why is it as it is rather than otherwise? The cosmological argument is the family of arguments that answers these questions by inferring from features of the observed world to a first cause, an unmoved mover, or a necessary being whose existence does not itself require explanation.

The argument is distinct from the ontological argument in starting from empirical premises rather than from the concept of God. It is distinct from the teleological argument (the argument from design) in starting from the existence rather than the apparent design of the world. Across its major versions — Aristotelian, Islamic, Thomist, Leibnizian — the cosmological argument has been the most widely defended philosophical argument for God's existence in the Western tradition.

The core claim

The core claim has three parts:

Some features of the world demand explanation. The world contains motion, causation, change, contingent beings that come to be and pass away. These features cannot be self-explanatory; they call for an explanation outside themselves.

The explanation cannot regress infinitely. A chain of explanations that contains no termination explains nothing. The argument requires that the explanatory chain terminate in something whose existence does not itself require external explanation.

The termination is what we call God. The first cause, the unmoved mover, the necessary being is identified with God. The identification typically requires further argument to show that the terminating principle has the attributes traditionally ascribed to God (one, simple, eternal, personal).

History in one paragraph

Aristotle gave the first systematic version in Metaphysics Book Lambda, arguing from the eternity of motion to an unmoved mover. The Islamic philosophical tradition developed the argument through Avicenna, whose proof from contingency (the burhān al-ṣiddīqīn) in the Kitāb al-Shifā' (c. 1014–1020) became the dominant version in medieval philosophy. Thomas Aquinas gave five versions in the Summa Theologiae Ia q.2 a.3 (the Five Ways), three of which (from motion, from efficient causation, from contingency) are cosmological in structure. Leibniz formulated the argument in terms of the principle of sufficient reason in the Monadology (1714) and the On the Ultimate Origination of Things (1697). Hume gave the canonical critique in the Dialogues Concerning Natural Religion (1779). Kant gave a parallel critique in the Critique of Pure Reason (1781). The argument was widely treated as defeated through the nineteenth century and revived in the late twentieth century through William Lane Craig's The Kalam Cosmological Argument (1979), Alexander Pruss's The Principle of Sufficient Reason (2006), and the analytic Thomist revival of the Five Ways through Edward Feser, Brian Davies, and others.

Aristotle's unmoved mover

The Aristotelian version proceeds from the eternity of motion. Motion in the cosmos is eternal. Every moving thing requires a cause of its motion. An infinite regress of moving causes does not explain the motion of the chain. So there must be a first cause of motion that is not itself moved — an unmoved mover.

The unmoved mover, in Aristotle's account, moves not by mechanical contact but by being the object of desire and contemplation for the cosmos. The cosmos is moved by the unmoved mover as an object of love is moved by its lover. The unmoved mover is pure actuality (energeia), without potentiality, and engaged eternally in contemplation of its own perfect activity — thought thinking itself.

The Aristotelian unmoved mover is identified with the divine but is not the personal creator God of the Abrahamic traditions. The cosmos was not created (it is eternal); the unmoved mover does not act on the world from above but draws it from above as an object of desire. The medieval reception transformed the argument by integrating it with the Abrahamic doctrines of creation and divine providence.

Avicenna's contingency proof

Avicenna's proof from contingency — the proof of the sincere — is one of the most influential single arguments in medieval philosophy. The structure: every being either has its existence necessarily (its essence includes its existence) or contingently (its essence is distinct from its existence). Contingent beings require a cause for their existence; the cause cannot itself be contingent; so there must be a Necessary Existent (wājib al-wujūd) whose essence is to exist.

The Avicennian argument differs from the Aristotelian unmoved mover in its starting point (the contingency of beings, not the motion of the cosmos) and in its terminating principle. The argument shaped subsequent Christian and Jewish natural theology; Aquinas's third way is a direct development of the Avicennian proof.

Aquinas's Five Ways

Aquinas presents five ways in the Summa Theologiae Ia q.2 a.3. The first three are cosmological in structure: the way from motion (parallel to Aristotle), the way from efficient causation, and the way from contingency (parallel to Avicenna). The fourth way (from degrees of perfection) and the fifth way (from final causation) have different structures.

The Thomist versions are compressed; each is presented in a single paragraph and assumes background metaphysics that Aquinas develops elsewhere. Each terminates with the formula this everyone calls God.

The contemporary analytic Thomist revival has extended the Five Ways. Edward Feser's Aquinas (2009) and Five Proofs of the Existence of God (2017), Brian Davies's The Thought of Thomas Aquinas (1992), and Eleonore Stump's Aquinas (2003) provide the major contemporary statements.

Leibniz and the principle of sufficient reason

Leibniz's version in the Monadology and On the Ultimate Origination of Things proceeds from the principle of sufficient reason: every fact has a sufficient reason for being so rather than otherwise. The existence of the world is a fact that requires a sufficient reason; the reason cannot lie within the world; so the reason must lie outside the world, in a being whose existence is necessary.

The Leibnizian version makes explicit the role of the principle of sufficient reason that the earlier versions had implicitly assumed. The strength of the argument depends on the strength of the principle.

Contemporary defenders (Alexander Pruss, Joshua Rasmussen, Robert Koons) have produced recent work on the principle of sufficient reason and its bearing on the cosmological argument.

Hume's critique

Hume's Dialogues Concerning Natural Religion (composed 1750–1770s, published posthumously 1779) gave the canonical eighteenth-century critique. The character Philo presses several objections: the move from observed causation in the world to a first cause of the world illegitimately extends causal reasoning beyond its empirical warrant; even granting a first cause, the argument does not establish that the first cause has the attributes traditionally ascribed to God; the principle that the chain of causes cannot regress infinitely is not self-evident; the existence of the world might itself be self-explanatory in ways the argument does not consider.

Hume's critique shaped the subsequent reception. The argument was widely taken to have been defeated through the nineteenth century, though the force of Hume's objections has been continuously contested.

Common confusions

The cosmological argument is not a single argument but a family. The Aristotelian, Avicennian, Thomist, Leibnizian, and Kalam versions have different structures and vulnerabilities. A critique that defeats one version may not defeat another.

The argument does not require that the universe began to exist. Most versions are compatible with an eternal universe. The Kalam version (developed by al-Ghazālī and revived by Craig) is the exception that does turn on a beginning.

The first cause is not the first member of a temporal sequence. In most versions, the first cause is first in the order of explanation, not in the order of time.

Live debates

Whether the principle of sufficient reason holds without exception. Contemporary defenders (Pruss, Koons) argue for strong versions; critics (van Inwagen, Bennett) argue that the principle either has obvious exceptions or leads to necessitarianism.

Whether the Big Bang cosmology supports the Kalam version. Craig's revival of the Kalam argument draws on twentieth-century cosmology. Critics (Smith, Grunbaum) dispute the inference from physical cosmology to the metaphysical premise.

Whether the argument, even if successful, establishes the existence of God in any traditional sense. Getting from a first cause to the personal, perfectly good, omniscient God of theism requires additional argument that the cosmological argument by itself does not provide.

Contemporary engagement

The contemporary literature is substantial. William Lane Craig's The Kalam Cosmological Argument (1979), Alexander Pruss's The Principle of Sufficient Reason (2006), Joshua Rasmussen and Alexander Pruss's Necessary Existence (2018), Edward Feser's Five Proofs of the Existence of God (2017), and Brian Davies's work on Aquinas constitute the major recent defenses. Major critical work includes Graham Oppy's Arguing about Gods (2006), Jordan Howard Sobel's Logic and Theism (2004), and the work of Wes Morriston. The Philosophy of Religion journal, the International Journal for Philosophy of Religion, and the Faith and Philosophy journal anchor the continuing scholarship.

Further reading

• Aquinas — the canonical Christian formulator
• Avicenna — the canonical Islamic formulator
• Aristotle — the originator of the unmoved mover version
• Hume — the canonical critic
• Ontological Argument — the other major argument for God's existence
• Problem of Evil — the major argument against God's existence
• Principle of Sufficient Reason — the metaphysical principle that grounds the Leibnizian version
• Five Ways — Aquinas's compressed presentation

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