QM works even if there are no humans or other subjective "observers". Any theory of QM that involves subjective observers for wavefunction collapse is quantum woo.
Suppose you are making a universe. You want to ensure that the universe you make is interesting, i.e. contains consciousness. So you set up the rules like QM: everything exists in probabilistic superposition until a consciousness observes it. One of the superpositions contains a consciousness, and that collapses the wavefunction guaranteeing consciousness in your universe. It's a way of using survivor bias in your favor.
Disclaimer: not to be taken seriously.
Disclaimer #2: Also, coincidentally, not related to poster drdeca. Unless he is me from another superposition and we haven't collapsed yet because you all are not as conscious as you think.
I suspect one could think of QBism as a theory of rational belief for agents in a context where details of quantum mechanics are highly relevant.
Just as bayesianism is a theory of rational belief more generally.
Perhaps we are using “theory of” in different ways?
How do you know?
I agree! However:
> because the vast majority of data we have excludes it
No it doesn't. In fact, there is not a single experimental result that rules this out and I doubt one could ever devise such an experiment in the first place.
All experimental results are consistent with the observer modeling the universe with the Schrödinger equation (i.e. with unitary time evolution / without collapse) and assuming that a measurement by said observer makes the wave function collapse to the appropriate eigenstate.