QBism, a Subjective Way to Take Ontic Indeterminism Dead Seriously

The term QBism, invented in 2009, initially stood for Quantum Bayesianism, a view of quantum theory a few of us had been developing since 1993.  Eventually, however, I. J. Good's warning that there are 46,656 varieties of Bayesianism came to bite us, with some Bayesians feeling their good name had been hijacked.  David Mermin suggested that the B in QBism should more accurately stand for "Bruno", as in Bruno de Finetti, so that we would at least get the variety of (subjective) Bayesianism right.  The trouble is QBism incorporates a kind of metaphysics that even Bruno de Finetti might have rejected!  So, trying to be as true to our story as possible, we momentarily toyed with the idea of associating the B with what Chief Justice Oliver Wendell Holmes Jr. called bettabilitarianism.  It is the idea that the world is loose at the joints, that indeterminism plays a real role in the world.  In the face of such a world, what is an active agent to do but participate in the uncertainty that is all around him?  As Louis Menand put it, "We cannot know what consequences the universe will attach to our choices, but we can bet on them, and we do it every day."  This is what QBism says quantum theory is about:  How to best place bets on the consequences of our actions in this quantum world.  But what an ugly, ugly word, "bettabilitarianism"!  Therefore, maybe one should just think of the B as standing for no word in particular, but a deep idea instead:  That the world is so wired that our actions as active agents actually matter.  Our actions and their consequences are not eliminable epiphenomena.  In this talk, I will describe QBism as it presently stands and give some indication of the many things that remain to be developed.

NOTE that Chris Fuchs' talk will follow one by Joseph Berkovitz (University of Toronto) on "A New Interpretation of De Finetti’s Theory of Subjective Probability" from 16:00 - 18:00 (more details at: http://www.mcmp.philosophie.uni-muenchen.de/events/calendar/index.html)