My problem with this line of reasoning is that it doesn't really prove that God exists so much as it proves that something caused the universe to exist, and then simply defines whatever that thing/phenomenon/event/reason/whatever was as "God." The argument doesn't demonstrate that this "God" is a thinking entity of any kind; perhaps the cause of the universe was some quirky phenomenon of physics that was no more of a God than quantum tunneling or virtual particles are "Gods." It also doesn't demonstrate that this "God" still exists, only that it existed at one time. You can't even demonstrate that this "cause" was a single thing. Perhaps the cause of the universe was a complex intersection of different phenomena and circumstances that allowed the universe as we know it to come into existence. My computer exists, and since according to Kalam everything that exists must have a "cause," there must be something that caused my computer to exist, but you would have a hard time pointing at any one thing as being the "cause"; you could give a complex description of various factories in SE Asia that manufacture computer parts, decisions by the good people at the Sony corporation to design a new computer and fund its construction, the history of semiconductor research over the last 70 years, Charles Babbage, and capitalism. You could then lump all that together as the "cause" of my computer existing and even label that collective mess of circumstances and motivations it as "God" if you want, as proof that "God" exists...for a very specific definition of God. There's not even any need to use something as grand as the cause of the universe when making this sort of argument, you can do it with anything: 1. Everything that moves must be caused to move by something. 2. There is a ball moving across my living room. 3. Therefore, something caused that ball to move across my living room. 4. That cause is God. Look, I just proved that God exists...for a very specific definition of God. Why does Kalam's argument seem interesting when mine seems stupid? Mine seems stupid because you can easily come up with any number of explanations for the cause of a moving ball that are not at all what people mean when they say "God," so it seems stupid and arbitrary to label them as "God." But there is no apparent reason to think that the cause of the universe is any more satisfying of a "God" than the case of the rolling ball in my living room.