That the World Can Be Shaped: Quantum Bayesianism, Counterfactuals, Free Will

Of scientific theories, the philosopher William James once wrote, 'You cannot look on any such [theory] as closing your quest. You must set it at work within the stream of your experience. It appears less as a solution than as a program for more work, and more particularly as an indication of the ways in which existing realities may be changed. Theories thus become instruments, not answers to enigmas. We move forward, and, on occasion, make nature over again by their aid.' On this conception, a theory is not a statement about what the world is, but a tool, like a hammer, to aid in making the world what we want it to be. The world may resist, but to some extent it is malleable. The research program of Quantum Bayesianism (or QBism) is an approach to quantum theory that hopes to show with mathematical precision that its greatest lesson is the world's plasticity. With every quantum measurement set by an experimenter's free will, the world is shaped just a little as it takes part in a moment of creation. So too it is with every action of every agent everywhere, not just experimentalists in laboratories. Quantum measurement represents those moments of creation that are sought out or noticed. If this vision of quantum theory stands scrutiny, it will mean that modern physics itself already speaks of a humanistic world--a world of hope & struggle & possibility & change. That would be the project's enduring impact. To get there though, much work remains, both mathematical and conceptual. With JTF's aid we propose to augment ongoing efforts by financing a visiting researcher, Dr. Appleby.