At 02:55 AM 2014/01/03, Joseph Brenner wrote:
Happy New Year and Goodwill to all FIS'ers and distinguished guests!
I found the concept of Quantum Bayesianism as presented by Professor von Baeyer most interesting. From the point of view of bringing the subject-object balance back into physics it is very congenial to Logic in Reality (LIR). I have several criticisms of this approach, however, which I will try to make clear in the absence of any real skills in quantum mechanics:
1. QBism seems not to consider the option of using non-standard, non-Kolmogorivian probabilities to describe quantum and non-quantum nature, that is, with values >0 but <1.
2. It excludes the case, impossible by classical logic, but basic to physics and LIR, of a dynamic interaction between the subject and the object which allows both views ("belief" and "facts") to be partly true or better operative at the same time or at different times.
3. Since the QBism interpretation does not deal with points 1. and 2. above (also in the Fuchs, Mermin, Shack paper), it leaves the door open to an anti-realist interpretation not only of quantum mechanical reality, but of reality /tout court/ which must be based on and reflect the quantum 'situation'.

Sorry Joseph, but I don't understand your point 1. Could you expand?

On 3, I think all forms of Bayesianism not only leave the door open to antirealist interpretations, but are antirealist by their nature that subjective probabilities are what probabilities are (Hume was the first to declare this point, to the best of my knowledge). Bayes Theorem itself is not antirealist, and can be applied to systems both internally and externally. It is also a theorem of information theory that applies whether you take information to be a subjective interpretation or an objective intrinsic property of systems. But Bayesianism is subjective by tradition and largely (there are exceptions in applications of algorithmic information theory along Wallace's lines) by usage. I find that people get a visceral reaction to Bayesianism much like they do to generalized antirealism (as opposed to antirealism about a class of things, which everyone accepts). Before an examination of a (realist) thesis, another (antirealist) member of the examining committee joked to me that being a realist or antirealist must be genetic. It is certainly deep seated.


Professor John Collier                           
Philosophy and Ethics, University of KwaZulu-Natal, Durban 4041 South Africa
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