This, according to Wikipedia, is William Lane Craig's version. You have to admit that 4. is a remarkable show of confidence — brazenly stating that the cause is the God of Classical Theism. Why is the cause the God of Classical Theism? Because the God of Classical Theism chose to create the universe. So there!
- Whatever begins to exist has a cause.
- The universe began to exist.
- Therefore, the universe has a cause.
- This cause is the God of Classical Theism, and is a personal being, because He chose to create the universe.
But the main problem with the Kalām, as I see it, is premise 2. "The universe began to exist." What do we mean by "universe"? Do we mean everything, ever? If so, then "everything" must include all the supernatural entities that might possibly exist — in which case God began to exist, and therefore must, according to this argument, have a cause himself.
That's what the Kalām is designed to avoid, by claiming that everything — or "whatever" to use Craig's phrasing — that began to exist has a cause. It's only things that had a beginning that need to have a cause. It doesn't apply to God, because God has always been there, despite Craig's frequent claim that there's a problem with an infinite past. (Basically his argument goes like this: if there's an infinite past, then there must have been an infinite number of past events, so anything that existed in an infinite past must have undergone an infinite series of past events to get to the present day, which is impossible. Except for God, naturally, because he lives "outside time" in the land of special pleading.)
Clearly a definition of "universe" that encompasses everything, ever (including any gods), is incoherent when talking about causes, because the causes must be included in "everything" as well. If our definition is instead the whole of material reality that originated in the Big Bang, we're on firmer ground. But to say that the universe originated in the Big Bang does not necessarily imply that there was nothing "before" it. In as much as "before" can mean anything at all at the point of time and space coming into being, we have a problem: if there's no concept of time, the notion of causality is indeterminate, because causes necessarily precede effects. It's because of our concept of time that we're able to distinguish between effects and their causes. Without time, cause and effect are at best interchangeable, at worst nonsensical.
The Big Bang — the origin of the universe — can be better conceptualized as a point of transition. A transition from what, we have no way of knowing. Another universe in the Multiverse perhaps, or in one of those other dimensions postulated by string theory, or even from some similarly unknown realm of cyclic reversal. What we can say, however, is that the universe as we know it did not necessarily have a beginning before which there was nothing. Indeed the concept of "nothing" may itself be incoherent (which would, incidentally, make redundant the question of why there is something rather than nothing).
So the Kalām is no more than a disingenuous rephrasing of the premises in such a way as to counter the obvious response. What caused the universe? God did. So what caused God? Ah, God doesn't need a cause because (despite the aforementioned paradox of infinities) he never began. Well, the universe as we currently understand it doesn't need a cause either, because it too doesn't need to have had a beginning.
When I was a teenager the Steady State theory still held ground against the more controversial Big Bang theory. I remember Arthur C. Clarke being questioned about this on a radio phone-in show. His response was delightfully equivocal: "I favour the Steady Bang theory, which I give to you for free."