Using axioms which implement an idealized EPR-style quantum spin measurement experiment (and assuming relativity), the authors set out to prove that:

*If the choice of directions in which to perform spin 1 experiments is not a function of the information accessible to the experimenters, then the responses of the particles are equally not functions of the information accessible to them.*

They call this the Free Will theorem since we in practice assume experimenters are free to set up the experiment the way they wish. So, the authors are not proving free will exists, they are proving that

*if*free will exists at the human level,

*then*the outcome exhibited by elementary particles will also be free.

The proof seems fairly straightforward once one accepts the earlier Kochen-Specker theorem (it can’t be said that the spin values for each direction already exist prior to measurement).

Following the presentation of the proof, the authors show (by discussing a way to modify Bohm’s theory) that QM is logically consistent if one assumes the assumption of particles expressing free will in a relativistic framework. Next, they relax some of the idealized assumptions to establish the robustness of the result in a more real world context.

The next section discusses how this result furthers the process (earlier marked by the K-S theorem and Bell's Theorem) of making hidden variable theories unworkable. They also argue it is an obstacle for GRW-type collapse models.

Further tidbits:

The authors argue that it is incorrect to interpret EPR-style experiments as meaning there is faster-than-light communication between particles; the particles are entangled as a collective system, but one will not confirm the predicted correlation until the future measurement of the other member of the pair. This is congruent with the perspective of Smerlak and Rovelli’s recent paper which interprets EPR from the perspective of relational quantum mechanics (RQM).

In terms of interpreting quantum mechanics: the authors argue quantum states (between measurements) are merely predictors (with probabilities) of what will happen

*if*various measurements are performed. It is a mistake to ascribe concrete reality to the quantum states. This again is consistent with RQM’s perspective that it is the measurement events which are concretely real. The authors also state briefly that they don’t believe a conscious human mind is needed for collapse, but they don’t discuss in detail what they think is necessary. They think a future physics will explain what sort of “texture” surrounding a system will cause collapse.

The authors offer some philosophical remarks on free will. First, they remind the reader that they don’t claim to prove free will. They say “determinism, like solipsism, is logically possible.” They themselves do subscribe, however, to what a philosopher would call a naïve folk conception of libertarian free will. They don’t see how science could be taken seriously if its practitioners weren’t free to investigate nature by choosing what experiments to perform.

In any case, the linking of free will at the human level to free or spontaneous outcomes at the level of elementary quantum systems is an important result. It is also an especially appealing idea to a panexperientialist like me. While I appreciate the substantial problems which afflict the folk conception of free will, the results of this paper fit with my view that the conscious experience, intentionality, and (at least limited) free agency of human beings are all sourced from fundamental and ubiquitous properties of the natural world.

I also want to comment on a section toward the end entitled “Free versus Random?” It is extremely common to interpret QM as meaning the universe contains a fundamental indeterminism, but it is unusual to say it implies the existence of a fundamental freedom. Here’s a point the authors make in favor of the latter:

“Although we find ourselves unable to give an operational definition of either “free” or “random,” we have managed to distinguish between them in our context, because free behavior can be twinned, while random behavior cannot (a remark that might also interest some philosophers of free will).”

“Twinned” here refers to the entanglement of two particles. The measurement of the first of the twinned pair enables us to predict the outcome of the measurement of the second, so they aren’t individually random events. But I’m not sure this is a good argument: are we conflating the idea of a particle’s randomness with its independence? I’ll have to give this more thought.

I’m very interested in arguments which support my contention that the worldview implied by QM is richer and much more interesting than just classical physics plus an overlay of randomness. It isn’t just that the measurement outcome is random vs. determined. The quantum measurement event has intrinsically more to it than a classical billiard-ball notion of a causal event. It is an interaction between two systems where one system’s propensity toward an outcome is actualized by the second (measuring) system. I believe this actualization event or process carries with it the raw material of agency (as well as experience).