This may be a naive question, but... I know that quantum mechanics prescribes various possible paths given an initial and final state. But is there a principle that is responsible for predicting the necessity of an initial state to begin with? We have QM accounting for all the possible paths of a particle. But what creates the particle itself? Does String theory predict the strings themselves, or does it only predict how they propogate? As I understand it, M-theory predict the initial state of the strings themselves from higher dimensional object, membranes, etc. Does M-theory predict the creation of particles/strings from the expansion of space-time itself? Thanks.