#### fluidistic

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Consider the example of the probability for a UK male of 25 years of age to die within the next year. Clearly, this probability is well defined and exists regardless of whether person A and person B agree about it. We can get a rather good estimate thanks to statistics, for example. But it seems that this logic does not apply anymore in QM. It seems like according to QM logic, that probability is subjective and only depends on who you ask. It is not a well defined number that exists regardless of the observer(s).

I am trying to convince myself that such a thing is possible, but I am unfruitful thus far. What would be the point then to write down the Schrödinger's equation for a system and solve for ##|psi \rangle## if I can come up with any other wavefunction and claim that it solves the same problem as described by another observer?

Does the subjectivity of the wavefunction in fact imply that the Schrödinger's equation is subjective? Because once the Schrödinger's equation is properly settled, then its solution follows.

I feel like I'm missing something in order to understand Lubos Motl and I feel like he's right. I have also glanced Wigner's friend Wikipedia's article and the QBism viewpoint. I do not want to deal with interpretations unless it is absolutely required.

From what I have read, extracting information out of a system is a subjective thing (though I do not understand how). Arnold Neumaier claims that this is done via an irreversible interaction though Lubos Motl claims that this isn't necessarily true and that irreversibility is also subjective (because even in QM everything is reversible though the probability to go one-way might be extremely small and the threshold is subjective), but I think this is besides the point.

So I am entirely confused about ##|\psi \rangle##. Can someone shed some light?