Sabine Hossenfelder wrote an essay arguing that the free will doesn't exist even though she can't quite define the concept. To decide whether the free will "exists", I think it's almost necessary to define what this concept means. Wikipedia says:
Free will is the ability of agents to make choices unconstrained by certain factors. Factors of historical concern have included metaphysical constraints (such as logical, nomological, or theological determinism), physical constraints (such as chains or imprisonment), social constraints (such as threat of punishment or censure), and mental constraints (such as compulsions or phobias, neurological disorders, or genetic predispositions). The principle of free will has religious, legal, ethical, and scientific implications.So the free will is the ability to make choices so that the choice wouldn't be done by "someone else". What we mean is that other, alternative spacetimes with the same past but different future seem to be compatible with all the knowledge (there are options!) but the choice of one particular possibility or another isn't determined by factors that we consider "external" relatively to the agent whose free will we are discussing. The term "free will" has many levels that differ by the inclusiveness of the factors that we consider "external".
For example, we talk about the "free will" in the political sense. Citizens of free countries and/or honest scientists have (and need) the free will – the freedom to make decisions about their life and about their experiments that are not determined by others. Citizens of North Korea are mindless screws in a squeaking machine so they don't have the free will. Alarmed climate scientists don't have the free will, either; their decisions are dictated by the external "cause" so regardless of the evidence and their personal views, they behave in a way that has the potential to maximize the climate panic and to please Al Gore and his accomplices.
But in the philosophical context, we want to view these political considerations as trivial. A person's decision may be determined by other people's desires and rules. In that case, we want to ask about the free will of these more powerful people. Do they really have the ability to make the choices? Where does the ability come from?
These questions may look well-defined to a philosopher (and to Sabine Hossenfelder) but they still fail to be well-defined according to a careful physicist. A careful physicist insists that at least in principle, there has to exist an operational definition of the free will – a procedure that decides about the answers to these questions operationally. And it's a problem. At most, in physics, you are allowed to decide whether some outcomes are determined/affected by or correlated with some other factors. You don't want to personify these factors or assign them with a thick layer of emotions and political labels because those are unphysical.
Moreover, if we don't want our thoughts about the free will to become vacuous, we must stop asking "why" at some moment. Arthur Schopenhauer has famously said "Man can indeed do what he wants, but he cannot will what he wants" (Einstein has loved that quote since he was a kid, and so did I). We might say that I went inline skating yesterday because I wanted – a manifestation of the free will – but one could still ask "who" or "what" determined that I wanted to go inline skating. Was it me or something else? Or something external? For the purposes here, it's enough for the free will to be able to "do what we want" even though we can't "will what we want". ;-)
In the framework that is close enough to the physical reasoning, we may define the free will by various correlations between the phenomena. For example, we may define the free will as the
"ability to circumvent or violate the laws of Nature – both the strict deterministic laws we knew in classical physics and the probabilistic laws provided by quantum mechanics".Sabine seems to have adopted this definition. I agree with her that the free will defined in this way doesn't exist. No one and nothing can violate the laws of physics. In classical physics, this sentence had the obvious strict meaning. In quantum physics, it means that phenomena (and, importantly, ensembles of phenomena) don't happen if quantum mechanics implies that their probability is a sufficiently insanely tiny number.
I can't really prove that her definition is a "wrong one" or an inconsistent one. But it still seems like an unwise, redundant one. The laws of physics have always applied in the Universe and most of the sensible people realized that they did. These people have still talked about the "free will". So I think that meaningful definitions of the free will shouldn't be in direct contradiction with the validity of the laws of physics.
(Let me mention that Sabine's opinion that the free will doesn't exist isn't just an innocent implication of her unwise definition of the term. She is a proponent of the superdeterminism, the ultimate conspiracy theory that envisions a cosmic dictatorship that really prevents experimenters from deciding to measure one quantity or another if the result could be an inconvenient truth for the cosmic dictator. I won't discuss this lunacy in this blog post.)
It seems much wiser to me to define the free will of a human or an object as
"the ability to pick one outcome from the list of at least two a priori possible outcomes so that the choice isn't a function of the whole past of the whole Universe with the object removed."I think that this is pretty much the definition adopted by Conway and Kochen in their free-will theorem: Wiki, TRF, arXiv. These thinkers have proven that if the experimenters enjoy the free will in this innocent sense, and sensible people think that they do (and this free will is necessary for science to be possible: see the point 10 at the very bottom of this blog entry), so do the elementary particles. This theorem doesn't imply that elementary particles are intelligent agents who should be treated just like humans, enjoy human rights, and/or be held accountable for their acts. But it means that the "random generator" choosing the outcome from a list of possible outcomes is "owned" by these particles. The outcomes are not determined elsewhere, in the rest of the Universe. The elementary particles contain whatever is needed to produce the outcome. The generation of the outcome may be associated with the region occupied by these particles.
Was there the free will according to classical physics? Well, it depends on what you mean by the word "external" that I discussed at the beginning. If you view all atoms of your body and your brain as "external stuff" that doesn't belong to you – and you want to define yourself as some kind of a "pure soul" – then indeed, there was no free will in classical physics. There were no souls, either. The atoms behaved (well, they were believed to behave) according to some deterministic laws.
These dust particles and small objects levitate not because they have the free will but because they are carried by the acoustic standing waves. Thanks to Gordon.
But you could also agree that the atoms in your brain "were" you. Then you had the free will according to classical physics because of some "locality": the motion of your mouth was indeed decided by the coordinates and momenta of particles that make up your brain. And these particles "were you" which is why "it was you who made the decisions". The decisions were done according to the values of the coordinates and momenta of the atoms – lots of numbers – but those numbers were what "defined what you were". You were these numbers. So if these numbers implied something, it was you who decided.
Some people can't swallow that "they are the numbers" which is the reason why they would say that they didn't have the free will according to classical physics. But the proposition "my identity isn't given by these numbers" is just an additional assumption, one that is in tension if not a direct conflict with the scientific thinking. I don't want to discuss the problem of the "free will" from the viewpoint of those who believe that the evolution of the Universe has nothing to do with any numbers because I think that these people are too stupid to deserve their spot on this blog.
In quantum mechanics, the outcomes of the measurements are only determined probabilistically which apparently "extends" the room for the free will. The random decisions are made by someone – a random generator (or a really, really good quasirandom one, but there is no known way how to replace the genuinely random numbers in quantum physics by quasirandom ones that wouldn't contradict other insights we have about Nature).
The free will theorem guarantees that these decisions are really made in the spacetime region where we observe them – the measured values can't be functions of some hidden variable that would live in the rest of the Universe. So the decision which keys I press (on the PB EasyNote keyboard whose keys A,C,F,N,alt seem to become insensitive at random moments) may be associated with processes inside my brain. In this sense, I have the free will. And electrons' whose spin turns out to be "down" and not "up" decided to have this spin themselves, too. The free will theorem is another theorem claiming that hidden variables cannot exist – but it selectively focuses on hypothetical hidden variables that would live in a particular region of the space (outside the subject or particle with the free will).
You see that according to the diagram above, your humble correspondent believes that physical determinism is false (well, the classical one is false: I mean that the right quantum theory is probabilistic) and the free will is possible which makes me a "libertarian". I don't quite see why these metaphysical views are correlated with the political ones but the result works pretty well, so it's OK. ;-)
Sabine discusses "ten misconceptions".
1. If you do not have free will you cannot or do not have to make decisions.Sabine disagrees with that because you can't avoid making decisions. Well, I think that the ability to make decisions is what should be called the free will – so I disagree with her view. They're just two ways to describe the same thing – both ways have the same additional ambiguities in their definition. A definition of the "free will" that can be non-existent even for objects that can make decisions seems meaningless to me.
2. If you do not have free will you have no responsibility for your actions.I don't know what to do with such things. The problem is that the term "responsibility for your actions" is a political phrase that is meant to be applied to human beings. It implicitly assumes all the human characteristics that people have, including the free will. If someone or something – like a mindless germ or a robot – does something that kills many people but if this killing was hardwired to them, we may say that the objects that caused the death didn't have the free will. Does it mean that they have no responsibility for the actions? Well, we may still better destroy the germ or the robot because it's dangerous. We do so regardless of these subjects' or objects' being animate or inanimate. The words about "responsibility" are just some extra emotions that we add to the comments, words that we sometimes say to the culprits because we assume that they're able to listen. But we usually don't chastise germs or robots. We think it's a waste of time. But their having done a bad thing may still have consequences. Operationally, the differences may be very small. Using the term "responsibility" only means that we think of the culprits as being human and similar to ourselves but there's no "objective" criterion that would say how much similar they have to be.
3. People should not be told they don’t have free will because that would undermine the rules of morally just societies.I partly agree with her. The society may work in pretty much the same way even if people say that they don't have the free will. After all, most people don't give a damn about these philosophical discussions, anyway. But those who do care may change their behavior. If someone suppresses the instincts and decides that everything is determined etc., he may become a nihilist or something else. Of course that such a change of the behavior is "irrational" in some sense. But the behavior dictated by the biological instincts (their previous behavior?) is arguably "irrational", too. So in practice, these changing collective beliefs about metaphysics may have social implications even though every individual can convince himself that the metaphysical debates may be disentangled from his behavior and goals.
4. If you do not have free will your actions can be predicted.Well, I defined the free will so that its absence means that the "choices apparently made by an agent" are functions of some external data which means that they can in principle be predicted. Of course, if one defines the free will in her way, the quote above is invalid. Things can't be predicted – the quantum randomness is genuinely random and lots of complex classical processes are unpredictable in practice, anyway, even though she defines the free will as something that cannot exist.
5. If you do not have free will the future is determined by the past.It's pretty much the same thing as the previous point and the same comments apply here, too.
6. If we do not have free will we can derive human morals.Pretty much independently of the free will, science cannot answer moral questions.
7. Free will is impossible.Her impossible "free will" is claimed to be possible now with the help of a preprint claiming that the laws of physics may belong to a "third group" which is neither deterministic nor probabilistic/random. I don't believe that there can exist any "third way" when it comes to the laws of physics so I disagree with her assertion here, too. The free will – if defined by a conflict with both deterministic and probabilistic laws of physics – is impossible.
8. You need to be a neuroscientist to talk about free will.Well, I mostly disagree with her in this point, too. Yes, neuroscience is just an application of physics etc. but it is also exactly the right level of science to discuss operationally meaningful yet nontrivial questions about the decisions and their origin. So the sentence above is largely true. You will be becoming a neuroscientist if you will be increasingly able to trace the origin of decisions etc.
9. You need to be a philosopher to be allowed to talk about free will.Well, I mostly agree: you don't have to be a philosopher to participate in these debates. But I would add that you have to be a philosopher of a sort not to realize that such talking about metaphysics is largely ill-defined and a waste of time.
10. If we do not have free will we cannot do science.I disagree with her, mostly. An experimenter must have a free will to decide what to measure in order for his conclusions to be undistorted. A researcher (a natural scientist or a crime investigator or anyone who was assigned similar tasks) whose investigation was controlled by some "external factors" that could have affected where the investigator looked and where he didn't (or where he looked more carefully or more often) is a corrupt researcher – much like researchers into "global warming" – and he cannot be trusted. One can't build any science out of this research. The results of the scientific research are only trustworthy if we assume that the experimenters are "independent" in the sense of the free will – and all the evidence we have is supporting the opinion that this assumption is valid.
P.S. While I don't think that Michio Kaku has answered all conceivable questions on the free will in this Big Think video (with half a million views), I would probably endorse this one in its entirety – which doesn't mean that I would endorse all of his videos, of course. ;-)