The cosmological argument is one of the oldest arguments attemping to prove the existence of God, through the existence of the universe, attempting to answer questions such as, "Why is there something rather than nothing?". The word 'cosmological' comes for the Greek word meaning order (of the universe). The forms of the argument are a posteriori as it draws upon observations and empirical evidence of the earth. Also the argument is inductive, meaning that the conclusion will be probable.
St Thomas Aquinas
St Thomas Aquinas proposed five ways to prove the existence of God. The first three of Aquinas' five ways support the cosmological arugument. His first effort (way) to confirm Gods existence is based on motion - the process by which an object acquires a new form. He suggests that nothing can move itself, given that nothing can be equally mover and moved, yet things are clearly in motion. He carried on to say infinite chain of movers cannot have a first mover, saying we cannot go back forever without arriving at a first cause. There, therefore, must be a first mover that causes motion in all things, and this we know as God.
Aquinas' second attempt (way) to prove the existence of God is based upon the uncaused causer. He states that the world is a series of events. All events are caused and nothing can be the cause of itself, Aquinas explains that this is therefore impossible. There must be a first cause on which all other causes depend on, formally known as the uncaused causer. If there were no uncaused causer then we could arrive at infinite regression, which for Aquinas is impossible because there cannot be no first cause. We cannot go backwards forever. Therefore there must be a cause of the whole sequence; God is therefore th cause of all that exists.
St Thomas Aquinas (2)
Aquinas' third way to prove the existence of God is based on observation (a posteriori) of 'Necessity and Contingency'. He states that some contingent beings exist, and while they exist, their non-existence is always possible. Therefore, contingent beings must depend on another being for their existence. The fact that we exist means that we depend on another being. This other being must have necessary existence and depend on nothing for its existence - it cannot not be. And as a result, a necessary being must exist, this being God.
In 1910, Gottfried Leibniz explained the cosmological argument in the form of the principe of sufficient reason. He put foward that even though the world has always been in existence, it would still need an explanation or sufficient reason for it's existence, which for Leibniz is because we need to establish something rather than nothing. In Leibniz's opinion, infinite regression is important because the universe is a specific thing and needs to be explained. The universe cannot go back forever, because otherwise we would arrive at an explanation.
Leibniz argued that even if we are sure the universe has always been in existence, and then there is nothing within the universe to show why it does exist as it is not self-explanatory. His argument pushes us to find an explaination of not just how things come into existence, but also why they do. For Leibniz, God is the explaination of the universe that doesn't depend on any futher explanation.
Professor Frederick Copleston' 'radio debate' was a broadcast in which he and Bertrand Russell discussed the cosmological argument. Copleston strongly supported the cosmological argument based on contingency and Leibniz's principle of sufficient reason. Copleston states that the totality of the world is comparised of contingent beings. There is no world distinct from these objects. Meaning that there are beings within the world that aren't self-explanatory. Therefore, the explanation for the world must be found externally to it. And that the reason must ultimately be an existent being that contains within itself the reason for its own existence. That reason is that it cannot not exist and that it is a necessary being - God.
Kalam cosmological argument
The Kalam cosmological argument dates back to medieval Muslim philosophers such as al-Kindi and al-Ghazali and has recently been resorted to popularity by William Lane Craig. Like all cosmological arguments, the Kalam cosmological argument is from the existence of the world to the existence of God and is an inductive argument. It rests on the idea that the world has a beginning in time and because of this notion that its existence is thought to stand in need of an explaination. The kalam argument states that everything that has a beginning has a course of its existence. The universe has a beginning of its existence - its finite and therefore the universe has a cause of its existence. If the universe has a cause of its existence, then this must be God.
David Hume - criticism
David Hume was an empiricist, a person who believes that the dominant foundation of knowledge is experience. When he came to consider causeation, he said that we couldn't experience the actual cause. Hume understood a 'cause' to be when two events follow each other and our minds make a connection between them. So the notion that experience is required for knowledge led Hume to argue that because we don't have any direct experience of the creation of the universe, we can't make conclusions about its creation. Therefore, if we use the cosmological argument, we go beyond our experiences and Hume would not allow this.
Hume also rejected the cosmological argument as just because we experience cause and effect within the universe, doesn't mean that the totality has a cause. In fact, Hume argued that when the parts are explained the whole is explained too. Additionally, Hume questionned whether the Universe had a beginning. He suggested that maybe it has always existed. In this case, it would be meaningless to ask about its cause.
David Hume - criticism (2)
Furthermore, Hume saw no reason to conclude that, even if the Universe did have a cause, that cause must be a christian God. The cosmological argument told us nothing of the attributes of the necessary being. And for this reason, Hume suggested that there could've been a committee of Gods for the cause of the universe.
Russell - Radio debate
Another key scholar who rejected the idea of the cosmological argument was Russell. he questioned the claim that there was a reson for everything. In particular, he challenged the idea that the universe needed an explanation. He went further, and said that any talking of the cause of the universe as a whole was meaningless.
Like Hume, Russell also rejected the argument that one cannot move from individual causes to the claim that the totality has a cause. He argued to say that every person who exists has a mother does not then imply that the human race has a mother. This is known as fallacy of composition.
Russell also claimed that the word 'necessary' could not meaningfully be applied to things. To say that something is necessary is to claim that it has to exist. However, Russell argued that to word existence is not an additional property. The word functions differently and therefore he concluded that there is no relationship between a concept and its actuality.
However, despite the many criticisms that have been raised against the argument, its strength as an a posteriori argument that draws on evidence that is universally available and that in itself cannot be challenged, gives the argument lasting appeal. The ultimate result of the cosmological argument is providing an explanation of the universe, not guarenteeing a correct one though.
Gottfried Leibniz explained the cosmological argument in the form of the principle of sufficient reason. The universe is finite and a specific thing, and as it stands it needs to be explained. For Leibniz, infinite regression is impossible. The universe cannot have always been in existence as by going back forever in time you are going to arrive at an explanation.
The sucess of the argument, however, is dependant upon the subject and whether they ask the question, 'Why is there something rather than nothing?' If you do not ask this question then the argument is invalid. In my opinion, i feel the argument is weak for the hypothesis that there is a God who created the universe, as the argument cannot explain God, only postulate God as the explanation.