This is half-intentional, as the problems with his argument have been pointed out many times before. But, to give the briefest of summaries for those who are unfamiliar: Krauss has pointed out that empty space contains vacuum energy, from which virtual particles can arise. It is not impossible, then, that the entire universe is a massive quantum fluctuation.
To be equally brief in criticizing him, it has been pointed out that, even though scientists often use the word “nothing” to refer to the quantum vacuum, it is not actually nothing. Moreover, this addresses only the Kalam, and is irrelevant to the other cosmological arguments.
I bring this up, however, because it is a good example of a common mistake. Philosophical arguments for God’s existence are often compressed into a scientific mold (often mangling them beyond recognition), then attacked for being poor science.
I’ll not deny that philosophical arguments are poor science, but one suspects that something has been missed here.
Using Krauss as an example, he clearly has compressed the Kalam (which is interested in the question “What is the original cause of physical reality?”) to “What caused the Big Bang?”. Thus, he thinks that by suggesting a cause of the Big Bang, he’s dealt with the argument, though the point being made is clearly not dealt with unless he can show that the quantum vacuum could itself be past eternal.
But the key point is that Krauss would never have made this mistake if he’d not assumed that a philosophical argument was an attempt at science.
Numerous attempts have been made to clarify these issues to Krauss and others. But, rather than speculate as to why they have failed, I’d like to make the point that one cannot press the idea that science will answer philosophical questions by simply assuming that these questions are scientific. That would, after all, be circular reasoning.
In fact, I think this is where we get the idea that there is some inherent conflict between science and religion. It seems more that there is a conflict between what is said in the name of science, and what is said in the name of religion. And a real conflict seems to depend on misusing one of the two of these disciplines.