Editing Wigner's friend (section)

===QBism and Bayesian interpretations===
In the interpretation known as [[QBism]], advocated by [[N. David Mermin]] among others, the Wigner's-friend situation does not lead to a paradox, because there is never a uniquely correct wavefunction for any system. Instead, a wavefunction is a statement of [[Bayesian probability|personalist Bayesian]] probabilities, and moreover, the probabilities that wavefunctions encode are probabilities for experiences that are also personal to the agent who experiences them.<ref name="healey">{{cite journal |last=Healey |first=Richard |title=Quantum-Bayesian and Pragmatist Views of Quantum Theory |journal=[[Stanford Encyclopedia of Philosophy]] |date=2016-12-22 |url=https://plato.stanford.edu/entries/quantum-bayesian/}}</ref> Jaynes expresses this as follows: “There is a paradox only if we suppose that a density matrix (i.e. a probability distribution) is something ‘physically real’ and ‘absolute’. But now the dilemma disappears when we recognize the ‘relativity principle’ for probabilities. A density matrix (or, in classical physics, a probability distribution over coordinates and momenta) represents, not a physical situation, but only a certain ''state of knowledge'' about a range of possible physical situations”.<ref>{{cite conference |last=Jaynes |first=Edwin T. |title=Inferential Scattering |book-title=Maximum-Entropy and Bayesian Methods in Inverse Problems |editor=Smith, C. Ray |editor2=Grandy, Walter T. Jr.  |year=1985 |publisher=Reidel |pages=377–398 |url=https://bayes.wustl.edu/etj/articles/cinfscat.pdf}}</ref> And as von Baeyer puts it, “Wavefunctions are not tethered to electrons and carried along like haloes hovering over the heads of saints—they are assigned by an agent and depend on the total information available to the agent.”<ref>{{cite book |last=von Baeyer |first=Hans Christian |title=QBism: The Future of Quantum Physics |year=2016 |publisher=[[Harvard University Press]] |isbn=9780674504646 |oclc=946907398}}</ref> Consequently, there is nothing wrong in principle with Wigner and his friend assigning different wavefunctions to the same system. A similar position is taken by Brukner, who uses an elaboration of the Wigner's-friend scenario to argue for it.<ref name="brukner">{{cite conference |last=Brukner |first=Časlav |author-link=Časlav Brukner |title=On the quantum measurement problem |series=The Frontiers Collection |arxiv=1507.05255 |book-title=Quantum [Un]Speakables II: 50 Years of Bell's Theorem |publisher=Springer |isbn=978-3-319-38985-1 |doi=10.1007/978-3-319-38987-5 |year=2017 |oclc=1042356376}}</ref>