9 Reasons Quantum Mechanics is Incomplete

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.

1. 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.
2. 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. (*) )
3. 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.
4. Statistical ensemble interpretation: Individual measurement outcomes exist, but QM has nothing to say about them. Therefore QM is incomplete.
5. Von Neumann collapse: Consciousness causes collapse, but nobody knows what consciousness is. Therefore QM is incomplete.
6. Objective collapse: One should add some additional terms to the Schrodinger equation, but there is no consensus on what these additional terms are. Therefore QM is incomplete. (*)
7. Many worlds: To derive the Born rule one needs some additional axioms, but there is no consensus on what these axioms are. Therefore QM is incomplete.
8. Consistent histories: All the allowed questions have unambiguous answers, but some questions are explicitly forbidden. Therefore QM is incomplete.
9. 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

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