[THANKS TO LAURIE PAUL FOR THE POINTER.]
Why is there something rather than nothing? How did there come to be something rather than nothing? Two different questions. A positive answer to the first, especially if a priori, implies that the second question has a false presupposition; if the reason is a priori, then it should have force at every moment of time, and this implies that there never could have been a moment when there was nothing. Conversely, if there is a positive answer to the second—if the Big Bang is an answer, for example—then there cannot be a positive reason for the first.
The two questions seem not to be distinguished by Lawrence Krauss, in a recent book, A Universe From Nothing: Why There is Something Rather Than Nothing.
The controversy is between David Albert and Lawrence Krauss. Krauss thinks that a situation in which there is nothing is at some fundamental level comparable to one in which there is something. Here’s how Albert puts it in the New York Times Book Review:
[Krauss’s view in Albert's words] According to relativistic quantum field theories, particles are to be understood . . . as specific arrangements of the fields. Certain arrangements of the fields, for instance, correspond to there being 14 particles in the universe, and certain other arrangements correspond to there being 276 particles, and certain other arrangements correspond to there being an infinite number of particles, and certain other arrangements correspond to there being no particles at all. . . . the laws of relativistic quantum field theories entail that [states in which there are no particles at all] are unstable. And that, in a nutshell, is the account [Krauss] proposes of why there should be something rather than nothing.
Albert thinks this simply changes the subject.
[Albert’s view] if what we formerly took for nothing turns out, on closer examination, to have the makings of protons and neutrons and tables and chairs and planets and solar systems and galaxies and universes in it, then it wasn’t nothing, and it couldn’t have been nothing, in the first place.
That’s one way of putting why Krauss hasn’t answered the why question. The states in which he thinks there is nothing are in fact states in which the “makings” of something exists.
Carroll’s take on the controversy is somewhat different. He seems to agree with Albert on what Krauss says:
[Carroll’s Take on Krauss: the 1st Possibility] if your definition of “nothing” is “emptiness” or “lack of space itself,” the laws of quantum mechanics provide a nice way to understand how that nothing can evolve into the marvelous something we find ourselves inside. This is interesting, and important, and worth writing a book about, and it’s one of the possibilities Lawrence discusses.
As against this, he says, there is the second possibility, namely that time itself is illusory. The space of possibilities is always the same, with the consequence that “moments” during which there is nothing (a la Krauss) are actually parts of a greater whole that exists timelessly. (Carroll doesn’t like this way of putting it, but it conveys the idea. It reminds me of Popper's "Parmenidean" take on Einstein.) If this is so, then:
[Carroll on the 2nd Possibility] Well, a bit of contemplation should reveal that this kind of reasoning might, if we grant you a certain definition of “nothing,” explain how the universe could arise from nothing. But it doesn’t, and doesn’t even really try to, explain why there is something rather than nothing — why this particular evolution of the wave function, or why even the apparatus of “wave functions” and “Hamiltonians” is the right way to think about the universe at all.
Unfortunately, Krauss doesn’t like this kind of philosophy. In fact, he doesn’t like philosophy at all:
[Krauss’s view] Philosophy is a field that, unfortunately, reminds me of that old Woody Allen joke, "those that can't do, teach, and those that can't teach, teach gym." . . . I'd say that this tension occurs because people in philosophy feel threatened, and they have every right to feel threatened, because science progresses and philosophy doesn't.
Oh well. That settles it then.