QBism, from Pragmatism to Phenomenology

QBism (pronounced “cubism”) is an interpretation of quantum mechanics that takes an agent’s actions and personal experiences as the central concerns of the theory.  This contrasts with the usual physicist talk of (passive) observers, macroscopically defined quantum measurements, and objective measurement outcomes or “clicks” available for all to see.  Moreover, the interpretation is distinguished by its use of a subjective Bayesian account of probabilities to understand the quantum mechanical Born rule (the means by which quantum theory calculates probabilities) as a normative addition to good decision-making.  In this sense the Born rule is not a law of nature dictating what the world must do, but a statement about how we each can strategize to best survive and prosper in an unruly, only partially controllable world.  Yet, the goal of physics has always been to say as much as we can about how the world is.  What is it about the world that compels this particular formalism for our best decision making?  This subject has been broached in three previous projects with STIAS, and this year we go at it again building upon our earlier explorations.  From these, a new direction has been spotted pointing to somewhere in between or around QBism’s roots in the American pragmatist tradition of William James and John Dewey and the yet-to-be-well-explored phenomenological philosophies of Edmund Husserl, Maurice Merleau-Ponty, and others.  How can such a deeply first-personal perspective as QBism and phenomenology expresses ever derive something solid about an ontology?  Our project will be to discuss these matters intensely among a select group of physicists and philosophers.

Project leader(s):
  • Christopher Fuchs (College of Science and Mathematics, University of Massachusetts Boston)
STIAS fellow(s):
  • Richard Healey (Department of Philosophy, University of Arizona)
  • Thomas Ryckman (Department of Philosophy, Stanford University)
  • Rüdiger Schack (Department of Mathematics, Royal Holloway, University of London)
  • Jacques Pienaar (Quantum Information and Quantum Matter Group, International Institute of Physics, Brazil) [Visiting Scholar]

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