Believe it or not, this is not very far off from physics. As harrachos stated, it was in response to a question. What's more, physicists routinely deal with what it means for space and time to exist (and one that has a beginning at that). There are many reasons not to believe in the existence of God, and Hawking is coming at it from a purely scientific standpoint: "Well, the concept isn't necessary, we're just making up a step to describe what we don't know." Whether or not you agree with his views, the fact is that science shows no reason for there to be either a God or an afterlife, and this is something I'm sure he's thought a lot about. Basically, logic and belief in God are deeply intertwined one way or another, so it's a natural side effect of his work.