The case against free will

Photo by Mark Neal, on Pexels

Laplace’s demon is a little character that occasionally pops up in the history of physics. Pierre-Simon Laplace wrote about it in 1814 to describe the deterministic nature of our universe. Imagine a sneaky demon, who somehow knows the position and momentum of every particle in the universe. This demon will be able to know exactly what the universe did at some earlier time and, more importantly, precisely what it’ll do at some later point. In other words, with perfect knowledge of the current state of the universe, it can determine what will happen at any point in the future.

The notion that our universe is deterministic is an intuitive one. When you throw something or hit a snooker ball, they follow a predictable path. Since Galileo and Newton, we know that all that’s needed to predict how a physical system will behave is some measurements and some calculations. It’s how we discovered Neptune and the reason we can predict with such accuracy when the moon will cross between us and the sun to produce a solar eclipse. Determinism tells us that Mars isn’t going to start going backwards, throwing off the probes that are en route and Voyager 1 won’t just give up one day and decide to come home.

However, the fact that matter in this universe doesn’t decide to do things is a problem because we are matter, and we regularly appear to make decisions.

Sure, we like to think we’re slightly more complicated than a hunk of rock or a robot, but fundamentally we’re still made of the same stuff. Whilst our brains may be some of the most complicated and intricate computational devices known to humankind, they’re ultimately just Hydrogen, Carbon, Nitrogen and Oxygen mashed together into a blob of wrinkly pink matter. Our wrinkly pink thinkers might have neurones, electrical signals, and synapses, but these comprise particles that must follow physical rules, just like everything else in the universe.

If we accept that the universe is deterministic, with every particle obeying physical laws, then our little demon — who perfectly knows the position and momentum of every particle that makes up your brain — should, in principle, know exactly what those particles will be doing in a second and in a few years, and for the rest of your life. Because the demon can calculate this with perfect precision, they can predict the thoughts that you’ll have and hence the actions that you’ll make. They can predict everything you will ever do. Even when we remove the imaginary demon from the equation, the fact that your brain and body are just a complex array of snooker balls whose movements could be calculated in principle means that there isn’t any room for you to say you have a choice.

There is no possibility for free will.

But hold on a second! What about quantum mechanics? In this wildly bizarre theory of very small things, that permits all kinds of strange phenomena, surely there’s some room to reintroduce free will? Quantum mechanics demonstrates that our universe is inherently non-deterministic and thus undermines the case for determinism and Laplace’s Demon’s omniscience.

Indeed, in quantum mechanics outcomes cannot be predetermined with certainty. Whilst there’s no consensus on the ‘correct’ interpretation for the seeming randomness of quantum behaviour, it is generally accepted that particles obey probabilistic rules as opposed to deterministic ones. However, herein lies the next problem. Probabilistic rules are inherently random. You might measure a particle with a 40% chance of doing one thing and a 60% chance of doing another, but prior to that measurement, there’s no ‘will’ for it to do either. In fact, quantum mechanics is almost the antithesis of free will precisely because states must occur randomly.

Quantum mechanics undermines determinism but simply replaces it with outcomes that cannot be known before measurement. Volition is predicated on a causal link between an intention followed by an action however, no such link can exist because there is no information that can reveal the outcome of a measurement before it is taken. Hence, at a quantum level, no mechanism can ‘will’ the outcomes of particle states that will ultimately lead to physical actions in the brain.

Of course, the possibility remains that there might be some additional unknown physics that permits free will. Perhaps there’s an intersection between the classical and the quantum that gives rise to freedom of choice. Perhaps the so-called randomness of quantum states is dictated by panpsychist microscopic intentions, or maybe this emerges when lots of quantum states are near each other.

This is, however, clutching at straws in the hope of preserving something that feels like it should exist. For one, the attribution of free will and hence consciousness to particles introduces more scientific and philosophical puzzles than it intends to solve. Furthermore, the likely decoherence of quantum states in the brain means that the classical, deterministic picture may be more appropriate after all. Even if we employ Occam’s Razor, it seems far more likely that free will is a simple illusion, no different to our brain filling in the gaps created by the blind spot in our eye, than it is a fundamental rewriting of the physics that governs the rest of the universe.

Of course, science has been wrong before, and our universe is vastly more complicated than we realise, but perhaps we truly don’t have free will. When you start to genuinely investigate that possibility in your mind, you might even start to see these deterministic and random processes at work. Your thoughts, actions and intentions all appear without genuine control, being created only through the mechanics of your brain.

So what if we don’t have free will? It’s easy to find ourselves powerless to change the course of our lives. But perhaps another viewpoint is to realise we’re all just actresses and actors. Everything we do is a pre-determined performance, with the lines written by nature and Laplace’s Demon sitting in the front row of the theatre. We can still experience the show too, seeing everything for the first time, but we don’t get to change the story.

You might disagree and maintain that we do have free will, which is completely fine. That’s just how the story was written and the role you were always meant to play. After all, it’s not like you have a choice.



Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store