#### Yazata

**Valued Senior Member**

QM is a statistical, mathematical system developed from a long history of observations to calculate the probabilities of occurrences in the quantum world.

I think that QM is kind of a paradigmatic example of an

**theory. It mathematically correlates observations. If you observe this, then you will observe that. Or in QM's case, you might have some predictable probability of observing that. That can be very useful for engineering purposes, it allows us to predict various kinds of phenomena and so on.**

*instrumentalist*What instrumentalist theories

**do is describe what's**

*don't***so as to produce the resulting observations. These kind of theories kind of reduce physical reality to a mysterious 'black-box' and only attempt to describe mathematical correlations between inputs and outputs.**

*actually physically happening*Hypothesizing as to what might actually be taking place inside the 'black-box' is where the countless extremely diverse

**of QM arise.**

*interpretations*Forrest already listed some of them:

--- Local hidden variables, Einstein and others

--- The Copenhagen interpretation

--- Many Worlds

--- Consistent histories

--- Ensemble interpretation, the statistical interpretation

--- de Broglie theory (local hidden variables, pilot wave)

--- de Broglie–Bohm (non-local hidden variables)

--- Relational quantum mechanics

--- Transactional interpretation

--- Stochastic mechanics

--- Objective collapse theories

--- Von Neumann/ Wigner interpretation: consciousness causes wave-function collapse

--- Many minds

--- Quantum logic

--- Quantum information theories

--- Modal interpretation quantum theory

--- Time-symmetric theories

--- Branching space–time theories

http://en.wikipedia.org/wiki/Interpretations_of_quantum_mechanics

It's important to notice that these various quantum mechanical interpretations presuppose very different ontologies. They imagine what actually exists in the universe and how it behaves, in dramatically different ways.

My own expectation is that future advances in the foundational levels of physics might eventually clarify a lot of this. And, just conceivably, as human beings gradually delve deeper into this stuff, not only will we achieve a far better understanding of what the physical universe really is, all kind of new and as-yet unimagined avenues of research and development might reveal themselves as well. (Just think about the implications of some of these QM interpretations, should they ever prove to be correct.)