— The Free Will Theorem n 2006, John Conway and Simon Kochen published The Free Will | Theorem. The paper received huge press attention and has been widely discussed in the scientific community. Their theorem states that; provided experimenters are free to run their experiment as they choose, the behavior of the particles they experiment upon is not determined in advance. Particles have free will! If we go back to the Bell Test experiment, this proved twin particles do not carry around a parcel of information telling them what to do. Perhaps they get their marching orders from some outside influence. There are two possibilities. A particle is either told what to do by its environment or it gets its information from some data source. Can we use the laws of physics to test these possibilities? We don't need to know how the influence works, just that it might exist in principle. Conway and Kochen prove there can be no external influence, and when a particle reveals its spin, that spin was not known beforehand. It is independent of any information in the history of the Universe up to that point. Conway and Kochen’s proof is elegant and involves some mental gymnastics, but it is no harder than Archimedes’ proof of the infinity of primes we looked at earlier. Let us start with our twin particles. We are going to pick bosons, which have whole number spin. If you measure the spin, you will always get a reading of -1, 0 or +1. ‘Spir’ is one of those words physicists use to explain quantum things. It does not necessarily denote rotation but, if your mental model is a spinning top, that’s not too HOUSE_OVERSIGHT_016033