I really like how John Horgan put that bigoted, pseudo-scientific, anti-religious tag team of Lawrence Krauss and Richard Dawkins in their place. The idea of offering the fact that quantum fluctuations can result in virtual particles becoming real as an answer to the question of why there is something instead of nothing is an insult to the intelligence of their audience, or worse, an appeal to their anti-religious prejudice as being sufficient to blind them to the absurdity of the proposition. As Horgan correctly rejoins, just where or where do the quantum fields that can give rise to virtual particles come from? Surely quantum fields are something and not nothing. Krauss’ thesis would be just plain silly if it weren’t so clearly intended simply as a rallying point for equally rabid atheists whose own pseudo-religious fervor trumps any appeal to reason and quest for truth.
I disagree with Horgan’s view that science is incapable of discovering an answer to that question but only, I think, because I prefer a broader conception of science than he apparently does. If by science we only include testable hypotheses then of course this question will always remain outside because there will never again be, if there ever were, a condition where literally nothing exists. Even if everything that is, ceased to be, there would always remain the fact that it had been. Besides, it would surely leave any test without anyone to observe the results.
I prefer to characterize science broadly as the search for knowledge about the nature of the world and that would include philosophy. I think if you construct a hypothesis which does not allow for testing but does permit you to make a reasonable assessment of probabilities, perhaps by eliminating the alternatives, or at least assessing them to be less likely, then that counts as science – especially if more narrowly scientific procedures can provide evidence that helps you make relevant assessments.