The physics
of free will

Michele Diego

The universe is a big clock, full of gears turning on each other in an orderly, predetermined manner.

Since the beginning of time, man has tried to explain why things happen. Today, in an age ruled by scientific thought, we describe the existence of lightning as caused by a difference in electrical potential between the ground and the clouds. There were once those who explained the phenomenon by attributing it to the wrath of Zeus or Thor. However different they may be, today’s approach and that of mythology have one thing in common: the all-too-human desire to explain why a phenomenon happens. Indeed, we live in a century in which we can convincingly explain a wide range of phenomena around us. We are aware of being inside a galaxy, around whose centre we orbit together with the entire solar system, where the planet we inhabit, Earth, in turn, orbits around the Sun. The force of gravity determines all these movements. Even on Earth, this force is fundamental: it holds back the atmosphere, it holds back the seas, and it holds ourselves and everyday objects from floating around freely. On a smaller level, things are mainly determined by electromagnetic forces: the cohesion of matter, the chemistry of different materials, and the transformation processes of food in the actions we accomplish. On an even smaller scale, it is nuclear forces that describe what happens inside atomic nuclei. In short, from galaxies down to atomic nuclei, everything is governed by well-defined laws, mathematically expressible forces, and cause-effect relationships. Being sufficiently well-informed about a system, we are able to predict its future by applying scientific laws. If we light a fire under a pot full of water, we know that it boils within a few minutes. If we throw a ball in the air, we know that it falls to the ground and, if we have enough information about the force of the throw and the mass of the ball, we can calculate exactly when it falls and where.

In the 19th century, Pierre Laplace imagined a demon capable of knowing the state of virtually all the particles in the universe, both their position and their speed. This demon, patiently applying the laws of physics, would be able to predict the entire future of the universe and even go backwards, tracing its entire past. As far as it is concerned, nothing surprising can occur because everything is already written and determined by precise and rational causes.
Laplace obviously knew that his demon was entirely imaginary. But for the French mathematician, its non-existence was merely a contingent, accidental fact: in his vision, there were no laws of the universe that would preclude its existence a priori. The universe is a big clock, full of gears turning on each other in an orderly, predetermined manner. Regardless of whether there was a creature capable of knowing every cog or not, did not change the nature of the universe itself.
But if every phenomenon in the universe can be traced back to a cause that precedes it and the entire sequence of universal events is already written, then why should the same not be true for us? Why should our actions and choices fall outside such predetermination? Why should our behaviour, our preferences, and our ideas, not be able to be traced back to the microscopic level, broken down into particles whose fate is dictated purely by cognisable deterministic forces?

If we imagine the world as Laplace imagined it – governed purely by exact mathematical laws – then there is no way out: the entire history of the universe is already written and we, as part of the universe, belong to that history. As such, free will does not exist. What we think of as a free choice has actually already been established billions of years ago. Particles, from the beginning of universal history, have followed a complex but preordained dynamic that has led them to make up our body today, as our thought, our choice, and our action.
Therefore, has it all already been decided and is there no escaping it? Pretty much, but there is a small consolation: Laplace was wrong. As a matter of fact, quantum mechanics predicts that there are a great many phenomena that occur randomly, which are impossible to determine with certainty. By ‘chance’, we do not mean the randomness of, say, tossing a coin, where in fact, on closer inspection, if one knew exactly the weight of the coin, the force to which it is subjected, the exact point at which that force is applied, one would be perfectly able to predict its outcome. In quantum mechanics, randomness is an intrinsic property of nature, it does not derive from the ignorance of those who observe the phenomenon without knowing it in sufficiently much detail. For example, if we observe a radioactive substance, it is impossible to predict the instant when a single atom of it will decay by emitting radiation. No one can predict this, not even a demon, because decay is an inherently random, statistical, probabilistic phenomenon. In addition, just like the decay of an atom, around us, at the quantum level, phenomena take place all the time with an outcome that is not predetermined a priori.
Have we therefore saved free will? Not exactly, and for two reasons. The first is that while it is true that one cannot know the outcome of many phenomena atom by atom, it is certainly possible to know on a statistical level what will happen on a macroscopic scale. Returning to the example of a radioactive substance, although one does not know the exact instant when each atom will decay, one can calculate with considerable accuracy – through statistical methods – how many atoms will have decayed after an hour. It is a bit like gambling: we may not be able to determine the individual fate of each player, whether they will come out triumphant or having lost everything, but we perfectly know how much the dealer will have earned by the end of the game. The second reason is that this quantum randomness is not a specific human feature. Even the atoms of a chair or a stone have quantum indeterminacies, thus trying to save free will through quantum indeterminacy means attributing free will also to objects such as a stone.

So how do we live with the awareness that our actions, our choices, which seem so free and personal to us, so poised before we make up our minds, actually stem from what happened in past events, even before we were born, even before the Earth existed? Many philosophers say that such awareness does not change the way we should behave one bit. I, however, do not know enough about philosophy to explain why this is so. However, man – as previously mentioned – seeks the reasons why things happen. So, yours truly invites readers to accompany him through the philosophical section of La Livella, and, finally falls silent.

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