Cosmological argument

A cosmological argument is a type of reasoning in the philosophy of religion that attempts to prove God's existence. It starts with observable facts about the universe—such as change, motion, or causation—and then examines these facts metaphysically. The universe is seen as either contingent (it could have not existed) or finite, which implies it needs something outside itself to explain its existence. Because this argument relies only on reason and observation, not on divine revelation, it belongs to the field of natural theology. It is also known as the argument from universal causation, the First Cause argument, or the prime mover argument.

The idea of causation is central to most versions of this argument, especially the claim that there must be a First Cause. This First Cause is identified through philosophical analysis as God, according to classical or other specific theistic views. Some versions treat the universe as contingent, meaning it has the potential not to exist and cannot explain its own existence. Others focus on the impossibility of an infinite chain of causes, motions, or past events, concluding that a First Cause or unmoved mover must exist.

The argument's origins go back at least to Aristotle. It was later developed in Neoplatonism, early Christianity, and medieval Islamic scholasticism (9th–12th centuries). Thomas Aquinas reintroduced it to Christian theology in the 13th century. In the 18th century, it became linked to the principle of sufficient reason, as articulated by Gottfried Leibniz and Samuel Clarke, which itself restates the Parmenidean principle that "nothing comes from nothing." Contemporary defenders include William Lane Craig, Robert Koons, John Lennox, Stephen Meyer, and Alexander Pruss.

**History**

**Classical philosophy** Both Plato (c. 427–347 BC) and Aristotle (c. 384–322 BC) offered cosmological arguments, but with important qualifications. In *The Laws* (Book X), Plato argued that all motion in the world and cosmos is "imparted motion" that requires a "self-originated motion" to start and sustain it. In *Timaeus*, he described a demiurge of supreme wisdom and intelligence as the cosmos's creator.

Aristotle disagreed with the idea of an efficient First Cause, because it contradicted his view of an eternal cosmos without a temporal beginning. His unmoved mover is a timeless being that sustains cosmic motion over an infinite duration, not an efficient cause that starts motion at a beginning. He proposed multiple unmoved movers, each powering a celestial sphere, dwelling beyond the sphere of fixed stars and subordinate to a Prime Mover (πρῶτον κινοῦν ἀκίνητον or *primus motor*), which is the ultimate source of all motion. In his "first philosophy" (metaphysics), Aristotle intended a theological link between the Prime Mover and a deity, but practically he was explaining the apparent motion of the fixed stars.

In Aristotle's natural theology, his eternal beings did not create the world or act on whims. He described the unmoved movers as timeless, immutable, purely actual, and purely thinking. Being immaterial, they cannot interact with the cosmos or know what happens in it. The celestial spheres, out of "aspiration or desire," imitate this perfection by moving in the most perfect way—uniform circular motion. The unmoved movers are the same in kind as the Prime Mover but subordinate to it through a dependency of relation.

**Late antiquity to the Islamic Golden Age** Plotinus, a third-century Platonist, taught that the One transcendent absolute caused the universe to exist simply as a consequence of its own existence (creatio ex deo). His disciple Proclus stated, "The One is God." In the 6th century, Syriac Christian neo-Platonist John Philoponus (c. 490 – c. 570) examined the contradiction between Greek pagan ideas of an eternal past and Aristotle's rejection of actual infinities. He categorized arguments for the finitude of the past, which supported his arguments for God's existence. Philoponus's ideas were later developed further by Muslim and Jewish exponents of kalam (medieval Islamic scholasticism).

In the 11th century, Islamic philosopher Avicenna (c. 980 – 1037) explored the question of being, distinguishing between essence (māhiyya) and existence (wuǧūd). He argued that existence cannot be inferred from or explained by the essence of existing things, and that form and matter alone cannot originate or interact with the universe's movement or the progressive actualization of things. Therefore, he reasoned, existence must come from an agent cause that necessitates, imparts, gives, or adds existence to an essence. For this to happen, the cause must coexist with its effect and be an existing thing.

**Medieval Christian theology** Thomas Aquinas (c. 1225 – 1274) adapted and improved the argument he found in Aristotle, Avicenna (the Proof of the Truthful), and Maimonides to create one of the most influential versions of the cosmological argument. His concept of the first cause was that the universe must be caused by something uncaused, which he called "that which we call God":

The second way is from the nature of the efficient cause. In the world of sense we find there is an order of efficient causes. There is no case known (neither is it, indeed, possible) in which a thing is found to be the efficient cause of itself; for so it would be prior to itself, which is impossible. Now in efficient causes it is not possible to go on to infinity, because in all efficient causes following in order, the first is the cause of the intermediate cause, and the intermediate is the cause of the ultimate cause, whether the intermediate be several or one only. Now to take away the cause is to take away the effect. Therefore, if there be no first cause among efficient causes, there will be no ultimate cause, nor any intermediate cause. But if in efficient causes it is possible to go on to infinity, there will be no first efficient cause, neither will there be an ultimate effect, nor any intermediate efficient causes; all of which is plainly false. Therefore it is necessary to admit a first efficient cause, to which everyone gives the name of God.