Philip hit on the fundamental difference between the two main “origin of the universe” paradigms when he said that some scientists believe that “nothing” never existed. It is philosophically possible that the laws of the universe have always existed (or, for multiverse enthusiasts, the laws behind the laws of the universes!). I remember somebody, possibly Lawrence Krauss, responding to the question “why is there something rather than nothing” with the reply “why not?” which is perfectly fair. However, the nature of “nothing” still needs clarifying. To claim that “nothing cannot exist” (as opposed to “nothing did once exist”) can only be justified in terms of what currently exists, which, of course, didn’t exist before the universe began.
I think Philip is wrong to say that the laws of QM or Gravity did not have to exist before they could operate. If they are only descriptions of what is, then they cannot describe how “what is” came into being. Although I think we must pop in a slight caveat here in that the term “before” is not really appropriate, in that “nothing” must also include no time, as well as no space, no matter and no energy.
However, before we think we have defeated the scientific philosophy that the universe could be spontaneously created “ex nihilo”, we must also consider that equally logically, “nothing” also includes “no God.” So even theologians must admit that there was never a real state of nothing at all.
Some philosophers are working around the idea that there is another fundamental constituent of the universe apart from matter and energy, which is “information”, and both scientists and theologians can come together in the idea that the nothingness from which the universe arose did include “information”. We could then both discuss the characteristics of this preceding “information”, based on the universe which seems to have emerged from it.