Here's an argument that the early modern philosophy Gottfried Wilhelm Leibniz gives for postulating the existence of an entity without parts, versions of which he gave from the 'middle' of his philosophical career--roughly, from about the time that he wrote the "Discourse on Metaphysics"--until the end, which, for present purposes, we can take to be the Monadology . Leibniz starts from the fact that material things can all be subdivided--he actually says that material things not only can be divided, but that they are actually infinitely divided. Since a material thing such as a table can be, as it were, decomposed into infinite material parts, Leibniz argues--in a line of reasoning that is especially emphasized in his correspondence with the philosopher Antoine Arnauld based on issues in the "Discourse on Metaphysics," but elsewhere in his writings as well--that a material thing like a table is no more metaphysically real than a heap of stones, a flock of sheep, or a rainbow: the basis for...

Not having read Hawking's book, I can't present _his_ answer; I'll try to respond to the question from the standpoint of someone who--as Hawking seems to do--thinks that theoretical physics is the ultimate explanatory authority. The question of where did the laws in virtue of which phenomena are to be explained come from amounts to the question of what explains why the particular laws of physics that apply to our world do apply to it. It seems to me that someone with Hawking's views would probably might that this simply is a question that we cannot answer at the moment: we lack the information necessary to give such an explanation, although, in principle, one could give such an explanation, and one might even--I can't do this, but someone else might--sketch the form that such an explanation would take. (I don't think that someone who shared Hawking's conviction could state conclusively that this is a question that cannot be answered: to do so would be to bet against science.) ...