I should warn you that I don’t know what on earth I’m talking about. On the other hand, nobody else does either. The question is, do we have free will or not?

What if I actually did raise my right arm? Would it prove that free will didn’t exist? What if we repeated the experiment hundreds of times, locking our predictions up in a safe, and I still ended up doing whatever you predicted?

Would life turn into one long episode of Early Edition? How often would you have to be ‘right’ to prove the theory that free will didn’t exist?

And what would be the alternative explanation? Would it be ‘scientific determinism’, the theory first advanced by Pierre Laplace that people could predict the future if only they knew the position and velocities of every particle in the universe…or would people simply think you were psychic?!

Einstein liked to come up with thought experiments to prove the likelihood (or absurdity) of scientific theories, either his own or those of other physicists, so here’s one for you. Free will implies that only I can determine my own intentions, so let’s see if that’s true.

If I asked you, “What am I going to do next?”, what would you say? You might say you had no idea, but that would simply accept the premise of free will as proof, which is a circular argument. If I pushed you for an answer, you might say I was going to raise my right arm.

If I then raised my left arm (or did anything other than raise my right arm), you might think that was ‘proof’ that you were right all along, but is that true? What if I had simply changed my mind?

That might itself demonstrate the exercise of free will, but you could always write down your prediction, and I could write down what I thought I was going to do, and we could compare the results afterwards. And this is where it gets interesting…

Laplace’s idea has now fallen foul of quantum theory. Specifically, the Heisenberg uncertainty principle states that you cannot measure a particle’s velocity and position simultaneously. Instead, particles are described by a wave function, which only indicates the probability of each value.

As I mentioned earlier, probability is problematic. It seems to imply an effect without a cause, and it also relies on the assumption that full information is not available, which it would be in this case.

Quantum physics only makes predictions at the atomic level, and it falls apart when dealing with objects at higher magnitudes such as stars and galaxies. Perhaps a hierarchy of explanations is needed, in which physics is the foundation of chemistry, which is the foundation of biology and then every other science in turn.

Whatever the outcome of that argument – and it’s been going on since at least 1905! – it certainly raises more questions than answers. Should people be held responsible for their own actions?

If so, why should criminals be allowed to plead ‘extenuating circumstances’? If not, why should they go to jail in the first place if it’s ‘not their fault’. Maybe Shakespeare was right, and character is fate, or maybe Shakespeare’s works were banged out by a monkey on a typewriter!

As Conan Doyle once wrote, “When you have eliminated the impossible, whatever remains, however improbable, must be the truth…”