Anybody who believes in reductionism and that the standard model of particle physics is correct to excellent precision must come to the conclusion that free will is an illusion. Alas, denial of this conclusion is widely spread, documented in many attempts to redefine “free will” so that it can somehow be accommodated in our theories. I find it quite amusing to watch otherwise sensible physicists trying to wriggle out of the consequences of their own theories. We previously discussed Sean Carroll’s attempt, and now Carlo Rovelli has offered his thoughts on free will in the context of modern physics in a recent Edge essay.
Free will can only exist if there are different possible futures and you are able to influence which one becomes reality. This necessitates to begin with that there are different possible futures. In a deterministic theory, like all our classical theories, this just isn’t the case – there’s only one future, period. The realization that classically the future is fully determined by the presence goes back at least to Laplace and it’s still as true today as it was then.
Quantum mechanics in the standard interpretation has an indeterministic element that is a popular hiding place for free will. But quantum mechanical indeterminism is fundamentally random (as opposed to random by lack of knowledge). It doesn’t matter how you define “you” (in the simplest case, think of a subsystem of the universe), “you” won’t be able to influence the future because nothing can. Quantum indeterminism is not influenced by anything, and what kind of decision making is that?
Another popular hiding place for free will is chaos. Yes, many systems in nature are chaotic and possibly the human mind has chaotic elements to it. In chaotic systems, even smallest mistakes in knowledge about the present will lead to large errors in the future. These systems rapidly become unpredictable because in practice measurement always contains small mistakes and uncertainties. But in principle chaos is entirely deterministic. There’s still only one future. It’s just that chaotic behavior spoils predictability in practice.
That brings us to what seems to me like the most common free will mirage, the argument that it is difficult if not impossible to make predictions about human behavior. Free will, in this interpretation, is that nobody, possibly not even you yourself, can tell in advance what you will do. That sounds good but is intellectually deeply unsatisfactory.
To begin with, it isn’t at all clear that it’s impossible to predict human behavior, it’s just presently not possible. Since ten thousand years ago people couldn’t predict lunar eclipses, this would mean the moon must have had free will back then. And who or what makes the prediction anyway? If no human can predict your behavior, but a computer cluster of an advanced alien civilization could, would you have free will? Would it disappear if the computer is switched on?
And be that as it may, these distractions don’t change anything about the fact that “you” didn’t have any influence on what happens in the future whether or not somebody else knew what you’ll do. Your brain is still but a machine acting on input to produce output. The evaluation of different courses of action can plausibly be interpreted as “making a choice,” but there’s no freedom to the result. This internal computation that evaluates the results of actions might be impossible to predict indeed, but this is clearly an illusion of freedom.
To add another buzzword, it also doesn’t help to refer to free will as an “emergent property”. Free will almost certainly is an emergent property, unless you want to argue that elementary particles also have free will. But emergent properties of deterministic systems still behave deterministically. In principle, you could do without the “emergent” variables and use the fundamental ones, describing eg the human brain in terms of the standard model. It’s just not very practical. So appealing to emergence doesn’t help, it just adds a layer of confusion.
Rovelli in his essay now offers a new free will argument that is interesting.
First he argues that free will can be executed when external contraints on choice are absent. He doesn’t explain what he means with “external constraints” though and I’m left somewhat confused about this. Is for example, alcohol intoxication a constraint that’s “external” to your decision making unit? Is your DNA an external constraint? Is a past event that induced stress trauma an external constraint? Be that as it may, this part of Rovelli’s argument is a rephrasing of the idea that free will means it isn’t possible to predict what course of action a person will take from exclusively external observation. As we’ve seen above, this still doesn’t mean there are different future options for you to choose from, it just means prediction is difficult.
Then Rovelli alludes to the above mentioned idea that free will is “emergent”, but he does so with a new twist. He argues that “mental states” are macroscopic and can be realized by many different microscopic arrangements. If one just uses the information in the mental states – which is what you might experience as “yourself” – then the outcome of your decisions might not be fully determined. Indeed, that might be so. But it’s like saying if you describe a forest as a lot of trees and disregard the details, then you’ll fail to predict an impending pest infection. Which brings us to the question whether forests have free will. And once again, failure to predict by disregarding part of the degrees of freedom in the initial state doesn’t open any future options.
In summary, according to our best present theories of nature humans don’t have free will in the sense explained above, which in my opinion is the only sensible meaning of the phrase. Now you could dismiss this and claim there must be something about nature then that these theories don’t correctly describe and that’s where free will hides. But that’s like claiming god hides there. It might be possible to construct theories of nature that allow for free will, as I suggested here, but we presently have absolutely zero evidence that this is how nature works. For all we know, there just is no free will.
But don’t worry.
People are afraid of the absence of free will not because it’s an actual threat to well-being, but because it’s a thought alien to our self-perception. Most people experience the process of evaluating possible courses of action not as a computation, but as making a decision. This raises the fear that if they don’t have free will they can no longer make decisions. Of course that’s wrong.
To begin with, if there’s no free will, there has never been free will, and if you’ve had a pleasant and happy life so far there is really no reason why this should change. But besides this, you still make your decisions. In fact, you cannot not make decisions. Do you want to try?
And the often raised concern about moral hazard is plainly a red herring. There’s this idea that if people had no free will “they” could not be made responsible for their decisions. Scare quotes because this suggests there are two different parts of a person, one making a decision and the other one, blameless, not being able to affect that decision. People who commit crimes cause pain to other people, therefore we take actions to prevent and deter crime, for which we identify individuals who behave problematically and devise suitable reactions. But the problem is their behavior and that needs to be addressed regardless of whether “they” have a freedom in their decision.
I believe that instead of making life miserable accepting the absence of free will will improve our self-perception and with it mutual understanding and personal well-being. This acceptance lays a basis for curiosity about how the brain operates and what part of decision making is conscious. It raises awareness of the information that we receive and its effect on our thoughts and resulting actions. Accepting the absence of free will doesn’t change how you think, it changes how you think about how you think.
I hope that this made you think and wish you a nice weekend :o)