# 9 Reasons Quantum Mechanics is Incomplete

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I argue that all interpretations of quantum mechanics (QM) are incomplete, each for its own reason. I also point out that for some interpretations (those marked with (*)) this incompleteness is in fact a good thing because in principle this incompleteness may be resolved experimentally.

**Shut up and calculate, logical positivism:**It’s OK to talk about the meaning, it’s just not OK to talk about it when one is doing science. Therefore science is incomplete. Assuming that QM is a science, it follows that QM is incomplete.**Old Copenhagen:**There is a quantum micro world and there is a classical macro world. Therefore QM is incomplete. (It is not specified where exactly the borderline between micro and macro is, so even QM and classical physics together are incomplete. (*) )**QBism, relational and other information-based interpretations:**There is an objective reality out there, but QM has nothing to say about it. Therefore QM is incomplete.**Statistical ensemble interpretation:**Individual measurement outcomes exist, but QM has nothing to say about them. Therefore QM is incomplete.**Von Neumann collapse:**Consciousness causes collapse, but nobody knows what consciousness is. Therefore QM is incomplete.**Objective collapse:**One should add some additional terms to the Schrodinger equation, but there is no consensus what these additional terms are. Therefore QM is incomplete. (*)**Many worlds:**To derive the Born rule one needs some additional axioms, but there is no consensus what these axioms are. Therefore QM is incomplete.**Consistent histories:**All the allowed questions have unambiguous answers, but some questions are explicitly forbidden. Therefore QM is incomplete.**Bohmian mechanics:**Only fundamental objects have trajectories. For instance a phonon (the quantum of sound) doesn’t have a trajectory. It is not known yet what the fundamental objects are, so QM is incomplete. (*)

(*) This kind of incompleteness is in fact good, because different choices lead to different measurable predictions. In the Bohmian case see https://lanl.arxiv.org/abs/1811.11643

D

Theoretical physicist from Croatia

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