Stephen Hawking recently stated that we do not need God to explain where everything comes from. Theoretical physics can provide the answer. My question to Hawking is: How does he explain the laws that were functioning with the Big Bang? Where do these laws come from? Physical laws are predictable, orderly events on which we can rely. Science is about testing knowledge against stated criteria or laws. So why is reality knowable (having laws to uncover, to use to our benefit)?

I too have not read Hawking's book, but from reviews I've read Hawking's argument is based on a theory of multiple universes he develops as an application of brane cosmology, which is an application of membrame theory (or M-theory), which itself is a theoretical development from string theory. In extremely general terms, this theoretical perspective seeks to explain the physical constants and physical laws in our universe by appeal to the diversity of physical and constants throughout the set of universes within the "multiverse," which is conceived of something like a set of separate space-times each governed by a different physical laws and constants. Hopefully panelists with expertise in these esoteric areas can chime in with more details, but with respect to the "God question" the reviews I have read represent Hawking as arguing that the "structure" of the multiverse provides a satisfactory explanation of the existence of a space-time that contains the physical laws and constants of our...

To follow up on my earlier response: In the February 10, 2011 edition of the New York Review of Books , Steven Weinberg has an excellent review of Hawking and Mlodinow's book. The review, which is also published online at URL , addresses some aspects of your question -- and also contains some good information about the theories that Hawking and Mlodinow are attempting to popularize.

Is it possible to determine whether the laws of Physics as they are currently perceived will last indefinitely? Is there anything to prevent the nature of the universe changing so much tomorrow that reality as we know it breaks down?

Kant thought he had a strong answer to Hume, but this answer requires embracing a strange metaphysical doctrine of transcendental idealism that few have found palatable. Kant' s best discussions of this occurs in his Critique of Pure Reason . Suppose, however, that we reject "strange" answers like Kant's idealism, and suppose we also admit that we cannot prove that the laws of physics will remain unchanged in the future. There may still be strong reasons why we ought to believe that the laws of physics will be invariant, for example because this belief is necessary for motivating people to be moral or for motivating humans to conduct scientific investigations of the world. There are strands of both strands of argumentation--the "strange" idealistic one and the "practical" one about human motivation--in Kant's discussion of the systematicity of nature and the regulative use of reason in the first introduction to the Critique of Judgment.