In a recent book called A Universe From Nothing: Why There Is Something Rather Than Nothing, cosmologist Larry Krauss describes how our universe could have arisen naturally from a pre-existing structureless void he calls "nothing." He bases his argument on quantum physics, along with now well-established results from elementary particle physics and cosmology. In an afterword, atheist Richard Dawkins exults, "Even the last remaining trump card of the theologian, 'Why is there something rather than nothing?' shrivels up before your eyes as you read these pages."
Philosopher David Albert will have none of it. In a in the New York Times (David Albert, New York Times Book Reviews, March 25, 2012), he asks, "Where, for starters, are the laws of quantum mechanics themselves supposed to have come from?" Krauss admits he does not know, but suggests they may arise randomly, in which case some universe like ours would have arisen without a prescribed cause. In my 2006 book The Comprehensible Cosmos, I attempt to show that the laws of physics arise naturally from the symmetries of the void.
In any case, Albert asserts that it doesn't matter what the laws of physics are. They "have no bearing whatsoever on questions of where the elementary stuff came from, or of why the world should have consisted of the particular elementary stuff it does, as opposed to something else, or to nothing at all."
Krauss says that the reason there is something rather than nothing is that the quantum vacuum state is unstable. His theological and philosophical critics claim that what he discusses is not really "nothing." Krauss dismisses this criticism and says that the "nothing" of his critics is some "vague and ill-defined" and "intellectually bankrupt" notion of "nonbeing." Albert insists, "Krauss is dead wrong and his religious and philosophical critics are absolutely right."
In fact, Krauss's book is a good introduction to the latest in cosmology suitable for a layperson. If you, as Albert, do not find Krauss's philosophical or theological views congenial, you should read the book anyway because these views are typical among theoretical particle physicists and cosmologists. If you want to dispute them, you should at least know where they stand.
Clearly, no academic consensus exists on how to define "nothing." It may be impossible. To define "nothing" you have to give it some defining property, but, then, if it has a property it is not nothing!
Krauss shows that our universe could have arisen naturally without violating any known laws of physics. While this has been well known for a quarter century (see A Brief History of Time and Not By Design), Krauss brings the arguments up-to-date.
The "nothing" that Krauss mainly talks about throughout the book is, in fact, precisely definable. It should perhaps be better termed as a "void," which is what you get when you apply quantum theory to space-time itself. It's about as nothing as nothing can be. This void can be described mathematically. It has an explicit wave function. This void is the quantum gravity equivalent of the quantum vacuum in quantum field theory.
Krauss also describes how cosmology now strongly suggests that a "multiverse" exists in which our universe is just one member. So, the real issue is not where our particular universe came from but where the multiverse came from. This question has an easy answer: the multiverse is eternal. So, since it always was, it didn't have to come from anything.
Albert is not satisfied that Krauss has answered the fundamental question: Why there is something rather than nothing, that is, being rather than nonbeing? Again, there is a simple retort: Why should nothing, no matter how defined, be the default state of existence rather than something? And, to bring religion into the picture, one could ask: Why is there God rather than nothing? Once theologians assert that there is a God (as opposed to nothing), they can't turn around and ask a cosmologist why there is a universe (as opposed to nothing). They claim God is a necessary entity. But then, why can't a godless multiverse be a necessary entity?
Now, one might still ask why there is something rather than nothing, where nothing means nonbeing including the absence of God. Here at least we can provide a suggestion based on our knowledge of the quantum void. As Nobel laureate Frank Wilczek put it in a Scientific American article back in 1980 (Frank Wilczek, "The Cosmic Asymmetry Between Matter and Antimatter," Scientific American 243, no. 6 (1980): 82-90), which Krauss quotes, "Nothing is unstable."
The issues Albert raises are legitimate, but they can be addressed within existing physics and philosophical knowledge.