What is a Cosmological Argument for the Existence of God?

Generally speaking, we can think of arguments for the existence of God as falling under two main categories: cosmological and teleological (sometimes also called fine-tuning). Both sorts of argument appear as separate formulations of the so-called ultimate question, which 'starts off', as Swinburne puts it, with our observation of the existence of a complex physical universe (Swinburne, 2004, 133). The ultimate question can be formulated in two separate ways, namely: (i) why is there something rather than nothing? and (ii) why is the universe the way it is? The cosmological and teleological (or fine-tuning) arguments correspond to formulations (i) and (ii) respectively. Here, we shall be dealing exclusively with cosmological arguments. While all cosmological arguments seek to answer formulation (i) of the ultimate question, not all cosmological arguments are formulated in quite the same way. Very roughly speaking, there are two main sorts of cosmological arguments, deductive and infinite regress.  Deductive formulations of the Cosmological Argument (contemporary formulations of this argument go at least as far back as Leibniz) begin by establishing 1- There could have been something rather than nothing (i.e. no universe)  2- Because there could have been nothing rather than something, the fact that there is something wants explaining 3- Because the existence of the universe is contingent (see1) this cannot be explained solely by virtue of the fact that the universe exists 4- it must therefore be explained by virtue of the existence of something other than the universe itself 5- the explanation of its existence must therefore include the existence of another being 6- The existence of this being must be necessary 7- there is therefore a necessary being other than the universe which exists. Unsurprisingly, this necessary being other than the universe is God. The spirit behind deductive formulations of the cosmological argument can be summarised by Swinburne's claim that God is the simplest explanation for the existence of the universe (see Swinburne, 2004). This of course can be challenged in various ways. It is important to clarify what is meant by something as opposed to nothing. It may be the case that the existence of something is indeed necessary, because the existence of nothing is inconceivable. It might follow that God is indeed not the simplest explanation for the existence of the universe.  Infinite Regress Arguments, sometimes referred to as Islamic Kalam arguments after the Islamic philosophical tradition which discussed them in greatest depth, go at least as far back as Aristotle's Physics. There are two underlying assumptions behind this argument. The first is that nothing can exist without a cause. With this in mind, one must say that if the universe exists, it must have a cause. This cause cannot be explained in terms of physical explanations because what is in question here is the existence of the physical universe itself. According to these arguments, God is the best candidate for an explanation of the existence of the universe. This argument also assumes the impossibility of an infinite time-space continuum going backwards (it too must have a cause!). Enemies of the Kalam argument challenge this last assumption and argue for the logical separateness of the existence of matter and the existence of space and time. They support this challenge by appealing to contemporary physics, which holds that quantum vacuums (space-time continuums devoid of matter) are inherently unstable, meaning that these vacuums are eventually bound to develop matter in them. The separateness of the existence of time and space from the existence of matter could provide us with an explanation of the existence of the universe which does not appeal to an entity like God.