String theory takes quantum mechanics and tries to make it compatible with gravity. If it turns out to be a theory of everything then would it explain why our world is described by the laws of quantum mechanics?

I want to understand if the laws of quantum mechanics are the only logical possibility for a low-energy theory potentially derivable from a better understanding of string theory. The other possibility is that they are just strange laws that are discovered through experiments that can't be reached by pure theoretical reasoning.

Which of the two possibilities is more reasonable from a physics point of view and why?

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    $\begingroup$ Yes, quantum mechanics is the foundation of all of modern physics - condensed matter physics, nuclear physics, atomic physics, optics, molecular physics, particle physics, quantum gravity, string theory - and it is the only logically possible framework aside from classical physics (which is ruled out) that is worth mentioning. The fact that QM can't be any different has lots of aspects, see e.g. motls.blogspot.com/2013/04/… One may perhaps explain the connections of QM to other things but postulates of QM won't change again. Ever. $\endgroup$ – Luboš Motl Apr 22 '13 at 11:04
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    $\begingroup$ The question asks if there is a more fundamental theory behind quantum mechanics(QM). This is a huge subject starting with e.g. hidden variable theories, Bohm's pilot wave theory, 't Hooft's deterministic models, etc.; and continuing with the latest ideas of quantum gravity. Perhaps it would be more constructive if OP would ask about a concrete proposal that extends QM? Related: The reference frame, this and this Phys.SE posts. $\endgroup$ – Qmechanic May 6 '13 at 19:20
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    $\begingroup$ Conventional string theory assumes quantum mechanical axioms from the very beginning. $\endgroup$ – Qmechanic May 6 '13 at 23:51
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    $\begingroup$ I think this question should get reopend to obtain a nice and clear answer which clears all misconceptions up once and for all. $\endgroup$ – Dilaton Jul 12 '13 at 14:28
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    $\begingroup$ fyi question imported/ open on physicsoverflow. see also/ more/ further analysis in chat, toy models of qm $\endgroup$ – vzn Jan 17 '15 at 16:31