The title of Lawrence Krauss's book, A Universe from Nothing: Why There Is Something Rather than Nothing, might have led you to believe that the theoretical physicist had attempted to answer the question of why there is something rather than nothing.
Which might explain why theoretical physicist—and philosopher—David Albert felt the need to gently point out that no, in fact he hasn't answered that question.
But it seems that Krauss was claiming nothing of the sort. At least, that's what I glean from a recent interview. Here are some selected highlight (interviewer's words in bold):
On that note, you were recently quoted as saying that philosophy "hasn't progressed in two thousand years." ...
Well, yeah, I mean, look I was being provocative, as I tend to do every now and then in order to get people's attention. ...
I try to be intellectually honest in everything that I write, especially about what we know and what we don't know. If you're writing for the public, the one thing you can't do is overstate your claim, because people are going to believe you. ...
And so when I read the title of your book, I read it as "questions about origins are over." ...
Well, if that hook gets you into the book that's great. But in all seriousness, I never make that claim. In fact, in the preface I tried to be really clear that you can keep asking "Why?" forever. At some level there might be ultimate questions that we can't answer, but if we can answer the "How?" questions, we should, because those are the questions that matter. And it may just be an infinite set of questions, but what I point out at the end of the book is that the multiverse may resolve all of those questions. From Aristotle's prime mover to the Catholic Church's first cause, we're always driven to the idea of something eternal. ...
I don't ever claim to resolve that infinite regress of why-why-why-why-why; as far as I'm concerned it's turtles all the way down. The multiverse could explain it by being eternal, in the same way that God explains it by being eternal ...
What drove me to write this book was this discovery that the nature of "nothing" had changed, that we've discovered that "nothing" is almost everything and that it has properties. ...
If I'd just titled the book "A Marvelous Universe," not as many people would have been attracted to it.
Well, glad we've got that cleared up now. Why does the multiverse exist rather than n— ... erm ... nada, zilch, nuttin'? That's a question we can't answer. The multiverse just exists. It's eternal.