On the program I watched, the theistic response was similar to the objection William Lane Craig made in his review of Vilenkin's book: that's not really "nothing". In Vilenkin's model, for example, there is no space, time, matter or energy – but the laws of physics would still exist in some way. Aside from the obvious philosophical conundrums the idea inevitably raises, one could argue that even the mere existence of the laws of physics clearly constitutes something. Theologian John Dickson, on the panel with Krauss, made this objection:
Here is a physicist telling us about something that all of us think sounds something and saying by some magical change of the English language, no, it’s nothing and if you disagree with me then you don’t understand science. But there are scientists, leading scientists, who agree this ain't nothing. It’s a very complex and beautiful something. And I think Tim's point earlier is the key point. We live in a universe that operates according to these elegant, beautiful laws and when I read your book this week I was more convinced that that's the case. And this universe, operating according to these elegant laws, has produced minds that now understand the laws, especially this mind next to us. And so this, to me, all looks and this is not a proof for God but I’m just saying why a lot of people think the God thing has a lot going for it, the whole thing looks rational. The whole thing looks set up to be known.
I think the fuss over what is meant by "nothing" is missing the forest for the trees.
The philosophical idea of nothing – namely, absolute non-existence, which I'll refer to as "Nothing" with a capital "N" – is only relevant when you're asking questions like, "Why is there something rather than nothing?", or "Where did the universe come from?" But asking where the universe came from is to make the baseless assumption that the universe, indeed, came from something else. Says who? There's nothing in the laws of physics which suggests that the universe came from anything else – including Nothing. Physicists have never claimed that the universe came from "absolute non-existence".
The confusion was echoed another question directed at Krauss:
But Harold actually asked the question I think you were saying did the laws of physics equally spring from nothing? Fully formed into existence from nothing?This kind of fussing over "nothing" completely misses the point. In these quantum models, the universe does not come from anything – it simply is. In Vilenkin's model, for example, it is nonsensical to talk about the quantum void coming from something else – for there was no time for it to do so! Even if only the laws of physics existed, they would not have come from anything else, but would simply be. That is why these ideas in physics – and there are many such possibilities – are so compelling. The question vexing physicists is whether the universe had to have come from something else, or if it could be enclosed, described entirely with the laws of mathematics. And while we are not ready to declare that we know this to be the case, it is at least plausible that one or more such models could indeed described a self-contained universe. They make any role of a Creator utterly superfluous. Just as evolution showed that humans did not have to be designed with great care, so too do modern physics suggest that the universe may not have needed to be designed with great care.
I imagine, too, that part of the confusion stems from the word "universe". As Brian Greene discusses in his latest book Hidden Reality, "universe" doesn't just mean one thing anymore. We could be talking about the observable universe, a parallel universe, a multiverse, some sort of proto-universe (that quantum void mentioned earlier), or all of it together. I think that generally, physicists use "the universe" to refer to the observable universe. A "universe from nothing", the way Krauss or Vilenkin talk about it, means that the observable universe came from some kind of quantum process, which embodies the closest to Nothing that we can get in science.
Maybe the language is too confusing. Maybe armchair philosopher types are simply unwilling to consider that the concept of nothingness can be defined mathematically. Maybe physicists should start saying "an uncaused universe" or "a self-contained universe" instead of "a universe from nothing". But personally, I think the term "universe from nothing" is really just a rhetorical device used to explain complex, esoteric physics to laypersons like myself. As long as I can grasp the concept, the precise language used isn't something I deem worth fussing over. And that's just the problem with these theologians – they're so busy fussing over the semantics that they've lost sight of the broader concepts.