It is frequently stated that path integral formulation of quantum mechanics is equivalent to the more traditional canonical quantization. However, I don't think it is really true. I claim that, unlike canonical quantization, path integral quantization is not self-sufficient. That's because the path-integral formulation itself does not contain a notion of a quantum state living in a Hilbert space, nor it contains any substitute for it. Instead, a self-sufficient formulation of quantum mechanics using path integrals must borrow the notion of quantum states from the canonical quantization. For example, how would you derive violation of Bell inequalities from the path-integral formalism? I don't think you could do that. My central claim is also reinforced by the fact that I can't remember that I ever seen a relevant paper on FOUNDATIONS of quantum mechanics based on path integrals. If you do foundations of quantum mechanics then states (especially entangled states) play a mayor role, and for such purposes the path integrals are not sufficient. What do you think?