Weinberg says that "we want to know what's happening out there". But this is just the standard anti-quantum zealots' misunderstanding of the essence of quantum mechanics. Quantum mechanics says that all knowable things about the physical system must be obtained through a measurement whose outcomes are predicted via the Born rule. There is nothing else happening out there, at least nothing else knowable that is happening out there! So quantum mechanics does answer the question what is happening out there and the claim that quantum mechanics is incomplete in this sense is simply a lie.
Czech physicist and translator
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You can't define whole disciplines of science to agree with random constraints that you invented. Instead, the purpose of disciplines of science is to decide whether your assumptions about the Cosmos and other things are correct. If there is a disagreement between the best theory and your assumptions, it's your assumptions that are wrong according to science.
Perturbatively, fundamental strings are more fundamental than branes or any other objects. In that old-fashioned description, D-branes are "solitons" — configurations of classical fields that arise from the closed strings. They are analogous to magnetic monopoles — which may also be written as classical configurations of the "more fundamental fields" in field theory. In a similar way, D-branes' masses diverge for 𝑔→0. Non-perturbatively, D-branes and other branes are equally fundamental as strings. In fact, when 𝑔 is sent to infinity, some D-branes may become the lightest objects — usually strings of a dual (S-dual) theory. When we include very strongly coupled regimes (high values of the string coupling constant 𝑔), there is a brane democracy.