> Physics is pretty much as deep as you can go.

I don't think all physicists actually think that, or there wouldn't be nearly as much interest in and effort expended on things like interpretations of quantum mechanics, i.e. attempts to explain what quantum mechanics means at some level deeper than merely "here is quantum mechanics, and it makes testable predictions" (http://en.wikipedia.org/wiki/Interpretations_of_quantum_mech...).