The cosmological argument is an argument for the existence of God or a "First Cause". It is traditionally known as an "argument from universal causation", an "argument from first cause", the "causal argument", and also as an "uncaused cause" or "unmoved mover" argument. Whichever term is employed, there are three basic variants of the argument, each with subtle yet important distinctions: the arguments from causation, in esse and in fieri, and the argument from contingency.
Plato (c. 427–347 BCE) and Aristotle (c. 384–322 BCE) both posited first cause arguments, though each had certain notable caveats. Plato posited a basic argument in The Laws (Book X), in which he argued that motion in the world and the Cosmos was "imparted motion" that required some kind of "self-originated motion" to set it in motion and to maintain that motion. Plato also posited a "demiurge" of supreme wisdom and intelligence as the creator of the Cosmos in his work Timaeus. For Plato, the demiurge lacked the supernatural ability to create ex nihilo (out of nothing). It was only able to organize the ananke (necessity), the only other co-existent element or presence in Plato's cosmogony.
Aristotle also put forth the idea of a First Cause, often referred to as the "Prime Mover" or "Unmoved Mover" (πρῶτον κινοῦν ἀκίνητον or primus motor) in his work Metaphysics. For Aristotle too, as for Plato, the underlying essence of the Universe always was in existence and always would be (which in turn follows Parmenides' famous statement that "nothing can come from nothing"). Aristotle posited an underlying ousia (essence or substance) of which the Universe was composed, and it was this ousia that the Prime Mover organized and set into motion. The Prime Mover did not organize matter physically, but was instead a being who constantly thought about thinking itself, and who organized the Cosmos by making matter the object of "aspiration or desire". The Prime Mover was, to Aristotle, a "thinking on thinking", an eternal process of pure thought.
Centuries later, the Islamic philosopher Avicenna (c. 980-1037 CE) initiated a full-fledged inquiry into the question of being, in which he distinguished between essence (Mahiat) and existence (Wujud). He argued that the fact of existence could not be inferred from or accounted for by the essence of existing things, and that form and matter by themselves could not originate and interact with the movement of the Universe or the progressive actualization of existing things. Thus, he reasoned that existence must be due to an agent cause that necessitates, imparts, gives, or adds existence to an essence. To do so, the cause must coexist with its effect and be an existing thing.
Thomas Aquinas (c. 1225–1274 CE), probably the best-known theologian of Medieval Europe, adapted the argument he found in his reading of Aristotle and Avicenna to form one of the most influential versions of the cosmological argument. His conception of First Cause was the idea that the Universe must have been caused by something that was itself uncaused, which he asserted was God.
Many other philosophers and theologians have posited cosmological arguments both before and since Aquinas. The versions sampled in the following sections are representative of the most common derivations of the argument.
The cosmological argument could be stated as follows:
According to the argument, the existence of the Universe requires an explanation, and the creation of the Universe by a First Cause, generally assumed to be God, is that explanation.
A basic explanation of the cosmological argument could be stated as follows:
Currently, the theory of the cosmological history of the Universe most widely accepted by astronomers and astrophysicists today includes an apparent first event, the Big Bang, an expansion of all known matter and energy from an infinitely dense singularity at some finite time in the past. Although contemporary versions of the cosmological argument most typically assume that there was a beginning to the cosmic chain of physical or natural causes, the early formulations of the argument did not have the benefit of this degree of theoretical insight. The Big Bang theory, however, does not address the issue of the origin of the primordial singularity, so it does not address the issue of a First Cause in an absolute sense.
Plato's demiurge and Aristotle's Prime Mover each referred to a being who, they speculated, set in motion an already existing essence of the Cosmos. A millennium and a half later, Thomas Aquinas argued for an "Uncaused Cause" (ex motu), which he called God. To Aquinas, it remained logically possible that the Universe had already existed for an infinite amount of time and would continue to exist for an infinite amount of time. In his Summa Theologica, he argued that, even if the Universe had always existed (a notion he rejected on other grounds), there would still be the question of cause, or even of First Cause.
In the scholastic era, it was unknown whether the Universe had a beginning or whether it had always existed, at least in terms of that for which reason alone could account. As a matter of faith, the beginning of the world was believed by Christians. To account for both possibilities, Aquinas formulated the "argument from contingency", following Aristotle in claiming that there must be something to explain why the Universe exists. Since the Universe could, under different circumstances, conceivably not exist (contingency), its existence must have a cause - not merely another contingent thing, but something that exists by necessity (something that must exist in order for anything else to exist). In other words, even if the Universe has always existed, it still owes its existence to an Uncaused Cause, although Aquinas used the words "...and this we understand to be God.
Aquinas's argument from contingency is distinct from a first cause argument, since it assumes the possibility of a Universe that has no beginning in time. It is, rather, a form of argument from universal causation. Aquinas observed that, in nature, there were things with contingent existences. Since it is possible for such things not to exist, there must be some time at which these things did not in fact exist. Thus, according to Aquinas, there must have been a time when nothing existed. If this is so, there would exist nothing that could bring anything into existence. Contingent beings, therefore, are insufficient to account for the existence of contingent beings: there must exist a necessary being whose non-existence is an impossibility, and from which the existence of all contingent beings is derived.
The German philosopher Gottfried Leibniz made a similar argument with his principle of sufficient reason in 1714. "There can be found no fact that is true or existent, or any true proposition," he wrote, "without there being a sufficient reason for its being so and not otherwise, although we cannot know these reasons in most cases." He formulated the cosmological argument succinctly: "Why is there something rather than nothing? The sufficient reason [...] is found in a substance which [...] is a necessary being bearing the reason for its existence within itself.
His premise for confirming all of these points was this:
The Universe as we know it today is not the only Universe that can ever exist in time. We can infer it from the fact that the arrangement and disarray, the order and disorder, of the present Cosmos might have been otherwise. That it might have been different from what it is. That which cannot be otherwise also cannot not exist; and conversely, what necessarily exists can not be otherwise than it is. Therefore, a Cosmos which can be otherwise is one that also cannot be; and conversely, a Cosmos that is capable of not existing at all is one that can be otherwise than it now is. Applying this insight to the fact that the existing Cosmos is merely one of a plurality of possible universes, we come to the conclusion that the Cosmos, radically contingent in existence, would not exist at all were its existence not caused. A merely possible Cosmos cannot be an uncaused Cosmos. A Cosmos that is radically contingent in existence, and needs a cause of that existence, needs a supernatural cause, one that exists and acts to exnihilate this merely possible Cosmos, thus preventing the realization of what is always possible for merely a possible Cosmos, namely, its absolute non-existence or reduction to nothingness.
Adler concludes that there exists a necessary being to preserve the Cosmos in existence. God must be there to sustain the Universe even if the Universe is eternal. Beginning by rejecting belief in a creating God, Adler finds evidence for a sustaining God. Thus, the existence of a sustaining God also becomes grounds for asserting the creating activity. The idea of a created Universe with a beginning and, most likely, an end now becomes more plausible than the idea of an eternal Universe. Adler believes that "to affirm that the world or Cosmos had an absolute beginning, that it was exnihilated at an initial instant, would be tantamount to affirming the existence of God, the world's exnihilator.
The difference between the arguments from causation in fieri and in esse is a fairly important one. In fieri is generally translated as "becoming", while in esse is generally translated as "in existence". In fieri, the process of becoming, is similar to building a house. Once it is built, the builder walks away, and it stands on its own accord. (It may require occasional maintenance, but that is beyond the scope of the first cause argument.)
In esse (in existence) is more akin to the light from a candle or the liquid in a vessel. George Hayward Joyce, SJ, explained that "...where the light of the candle is dependent on the candle's continued existence, not only does a candle produce light in a room in the first instance, but its continued presence is necessary if the illumination is to continue. If it is removed, the light ceases. Again, a liquid receives its shape from the vessel in which it is contained; but were the pressure of the containing sides withdrawn, it would not retain its form for an instant." This form of the argument is far more difficult to separate from a purely first cause argument than is the example of the house's maintenance above, because here the First Cause is insufficient without the candle's or vessel's continued existence.
Thus, Aristotle's argument is in fieri, while Aquinas' argument is both in fieri and in esse (plus an additional argument from contingency). This distinction is an excellent example of the difference between a deistic view (Aristotle) and a theistic view (Aquinas). Leibnitz, who wrote more than two centuries before the Big Bang was taken for granted, was arguing in esse. As a general trend, the modern slants on the cosmological argument, including the Kalam argument, tend to lean very strongly towards an in fieri argument.
One objection to the argument is that it leaves open the question of why the First Cause is unique in that it does not require a cause. Proponents argue that the First Cause is exempt from having a cause, while opponents argue that it is not. The problem with arguing for the First Cause's exemption is that it begs the question of why the First Cause is indeed exempt.
Secondly, the premise of causality has been arrived at via a posteriori (inductive) reasoning, which is dependent on experience. David Hume highlighted this problem of induction and showed that causal relations were not true a priori (deductively). Even though causality applies to the known world, it does not necessarily apply to the Universe at large. In other words, it is unwise to draw conclusions from an extrapolation of causality beyond experience. Furthermore, the rules of causality only make sense in the context of time, which obviously did not exist before the creation of the universe, thus it is nonsensical to speak of "causes", specifically a First Cause, when discussing the origins of the universe.
Additionally, it is argued that Occam's razor can be used against the argument, showing how the argument fails using both the efficient and conserving types of causality.
Another objection is that even if one accepts the argument as a proof of a First Cause, it does not identify that First Cause with God. The argument does not ascribe to the First Cause some of the basic attributes commonly associated with, for instance, a theistic God, such as immanence or omnibenevolence. Rather, it simply argues that a First Cause (e.g. the Big Bang) must exist. Despite this, there exist theistic arguments that attempt to extract such attributes.
Furthermore, if one chooses to accept God as the First Cause, God's continued interaction with the Universe is not required. This is the foundation for beliefs such as deism that accept that a God created the Universe, but then ceased to have any further interaction with it.
The argument for a Prime Mover is based on the scientific foundation of Newtonian physics and its earlier predecessors — the idea that a body at rest will remain at rest unless acted upon by an outside force. However, while Newton's ideas survive in physics today, since they conveniently and easily describe the movement of objects at the human (that is, not cosmic or atomic) level, they no longer represent the most accurate and truthful representations of the physical Universe. Some scientists feel that the development of the laws of thermodynamics in the 19th century and quantum physics in the 20th century have weakened a purely scientific expression of the cosmological argument.
Modern physics has many examples of bodies being moved without any known moving body, apparently undermining the first premise of the Prime Mover argument: every object in motion must be moved by another object in motion. Physicist Michio Kaku directly addresses the cosmological argument in his book Hyperspace, saying that it is easily dismissed by the law of conservation of energy and the laws governing molecular physics. He quotes one of many examples — "gas molecules may bounce against the walls of a container without requiring anything or anyone to get them moving." According to Kaku, these particles could move forever, without beginning or end. So, there is no need for a First Mover to explain the origins of motion. It does not provide an explanation for the reason those molecules exist in the first place, though.
Moreover, it is argued that a challenge to the cosmological argument is the nature of time. The Big Bang theory states that it is the point in which all dimensions came into existence, the start of both space and time. Then, the question "What was there before the Universe?" makes no sense; the concept of "before" becomes meaningless when considering a situation without time, and thus the concepts of cause and effect so necessary to the cosmological argument no longer apply. This has been put forward by J. Richard Gott III, James E. Gunn, David N. Schramm, and Beatrice M. Tinsley, who said that asking what occurred before the Big Bang is like asking what is north of the North Pole. However, some cosmologists and physicists do attempt to investigate what could have occurred before the Big Bang, using such scenarios as the collision of branes to give a cause for the Big Bang.