In his latest book, The Grand Design, Stephen Hawking claims that the concept of God is not needed to explain the existence of the universe. The answer, according to him, is spontaneous creation: the universe created itself, by itself, spontaneously. Spontaneous auto-creation doesn't call for a creator.
In saying this, Hawking doesn't speak like a scientist: he speaks like a (speculative) philosopher. Scientists cannot say whether we "need" a God to explain the way the world is; all they can say is that science (and here mostly they mean physics) can (although so far it hasn't) find equations that account for all the laws of nature. Such a "theory of everything" would account not only for all the laws of nature, but for all the things that are governed by the laws of nature, that is, for the way all things are in space and time. And even for spacetime itself. This would be equivalent (Einstein said) to reading the mind of God. Only Hawking now says that God is not involved: as Laplace said before him, it's a hypothesis for which we no longer have any need.
But this is an old story -- an old fallacy. Hawking claims that the universe created itself by "spontaneous creation." But how come that the universe -- our particular universe -- created itself just the way it is? Was that "spontaneous creation" a lucky fluke? Pure serendipity? Could it not be that the universe has been created so it would create itself the way it is? Scientists know that our universe is a most unlikely place; statistically, it's entirely improbable. According to quantum string theory, there could be about 10500 possible universes (this is the number 1 followed by 500 zeros). Only a handful among this staggering number of possible universes could bring forth life, not to mention so-called higher forms of life where beings who consider themselves intelligent claim they and their world came about by serendipity.
To answer "why" our universe "created itself" the way it did is beyond science. To say that it did so spontaneously is not an answer: it's an excuse for an answer. When Hawking says that the spontaneous self-creation of the universe "out of nothing" is evidence that a creator was not involved, he is not speaking as a scientist. He is not making a scientific statement. His statement is pure theology -- of the negative kind typical of atheists.
To deny the existence of a transcendental creator is just as much an act of faith as to affirm it. Of course, we can speculate on this question, and we should speculate: who says that the limits of science must be the limits of human inquiry? But we should not claim that when we speculate we speak as scientists, even if we happen to be the author of the mind-boggling equations that account for the behavior and ultimate end of black holes.
In a recent post, "Why Some Religious People Fear (and Fight) Science -- And Why It's a Sad Mistake," I said that the religious have no reason to fear science, and I stand by that. I should point out, however, that I meant "science," and not -- and certainly not all -- "scientists."