Very early in the classic work of David Armstrong (A Materialist Theory of Mind) comes the expression, "the supremacy of physics." That is to say, Armstrong believes that all mental processes can be reduced to chemical processes which in turn can be reduced to processes described by physics. As my first-year physics tutors claimed: everything is physics, even chemistry is just dirty physics.
For Armstrong, descriptions by physics are the irreducible descriptions. We cannot split the universe into blocks smaller than those described by physics. Neither can we split human consciousness into anything more fundamental that that which can be described by physics. He does not say that this is the only valid way to describe it. After all, human consciousness can be discussed in terms of awareness, knowledge or thought. Human existence clearly includes emotions, social relations and physiology. However, all of these things, according to Armstrong, are merely layers built on top of fundamental descriptions from physics.
My undergraduate degree was in engineering, so this settles well with me. The irony is that at the time of studying for engineering, I was a fundamentalist pentecostal. Now that I'm studying theology, I'm a card-carrying Marxist. Figure that out for yourself.
But I digress. Armstrong's train of thought is a reasonable one in this age of knowledge and scientism. Unless something can be proven with some sort of scientific method, the contemporary Western mind will not accept it as anything truthful. It would be an opinion piece, or a religious text, and so on. Is truth only verified by physics? Not if you think that truth and fact are different things. Physics can verify a lot and as any serious physicist will tell you, there are still a great many questions yet to be answered by physics.
The gap between current knowledge of physics and a Grand Unified Theory of Everything is not, however, the limits of space for religion and God. It might be that the language we use for philosophy/theology is capable of describing things that occupy that gap better than physics can, but they should not form a dichotomy. There is no boundary between physics and philosophy/theology. The two should be treated as different layers of language used to describe the same cosmos. Philosophy/theology has nothing to fear from physics, and physics has nothing in philosophy/theology to attack. Ultimately, the two schools pursue the same thing: knowledge of the cosmos and a language with which to describe it.