On the problems with the cosmological argument
So if there was a Big Bang, something surely must have caused it, right? Or at least, be the explanation for this bang? And that, reasonably, must be God, right?
This is known as the cosmological argument. It's really an ancient argument, and many regard it as the most convincing argument there is for the existence of God.
I submit, though, that despite its popularity, this is argument is completely useless, and in this post I want to explain why.
What is a "cause"?
In my experience, whenever someone advances the cosmological argument, the first thing that happens is usually that someone points out that the idea of things "causing" other things rests on our intuition about physical time, and that for all we know there might note have been any "time" before the Big Bang. To quote Stephen Hawking, asking what came before the Big Bang could be as meaningless as asking what is north of the north pole. If there is no meaningful way in which we can speak of a "before" the Big Bang, we obviously cannot speak of a "cause" for the Big Bang - not a "cause" in the normal, temporal sense of the word, at least.
Perhaps the proponent of the argument will then say "Well, maybe it does not have a normal/temporal cause, but it can have some other kind of cause". But then you have better define what a "non-temporal cause" is, and convince me that the Universe must have such an non-temporal cause, which is not going to be easy.
I think this objection - the "cause-is-not-a-meaningful-concept-in-this-context"-objection, is valid. It shows that we can, plausibly, reject the premises of the cosmological argument. Unfortunately, discussions over these matters tend to end up being extremely long, very philosophical, and hard to follow. However, there is a much easier way to refute the cosmological argument.
Why should the supposed "ultimate cause" be a personal God?
Even if we accept the existence of a "cause" for the Universe, or even an "ultimate cause", or an "ultimate explanation", it does not follow that this ultimate cause/explanation must be a personal God. We have an explanation for why there is thunder and lightning, but that explanation is not Zeus or Thor.
In other words: we have no reason to ascribe, to this "ultimate cause", properties like sentience, omniscience, omnipotence, personal interest in us, prayer-answering, etc. And that's quite a showstopper for the cosmological argument: the whole point of the argument is to "prove" the existence of a personal God, not just some kind of "ultimate cause".
This is the big problem with the cosmological argument.
Logical necessity?
What then could a non-divine "ultimate cause" be?
Well, what if the Universe (and everything else that exists) simply exist out of pure logical necessity?
I imagine that people here will object that logic itself doesn't necessitate anything at all. It might, for example, seem perfectly possible, logically speaking, to imagine a situation where nothing exists. Why then is there something rather than nothing? Don't we need an explanation for that?
But actually, since the antiquities there have been philosophers (for example, Parmenides) who have argued that the idea of there being "absolutely nothing" is incoherent. For instance, we might argue that in order for any statement (including the statement "Nothing exists") to be true, we need to believe in the existence of the statement itself, as well as a truth-property which this statement has (as opposed to other, false statements). Thus, believing in the statement "Nothing exists" seems to present us with a paradox, as the only way for such a statement to be true is if there is something, namely statements and a truth-property. That is not "nothing".
Fact of the matter is, there is no consensus among philosophers, mathematicians, logicians and scientists on what "logic" really is. Profound discoveries, like Russell's Paradox and Gödel's incompleteness theorem, have shown that something still seems to be missing in our understanding of what logic is, and how we should interpret these results is debated still today. Thus, we cannot say, with any kind of certitude, that "logic" does not "necessitate" anything at all. It would seem, therefore, that for all we know, the Reality could indeed simply be a result of logical necessity.
Conclusion
In conclusion, then, the cosmological argument is really not impressive at all, and the most obvious way of seeing this is to note that we cannot really say anything about the nature of the supposed "ultimate cause", even if there would be such a thing. To say that this ultimate cause is a personal God, some other kind of argument is needed. In other words: the cosmological argument in itself doesn't make the existence of a personal God seem any more plausible, and as an argument for the existence of God it is therefore completely useless.