Sabine Hossenfelder argues
Physics deals with the most fundamental laws of nature, those from which everything else derives. These laws are, to our best current knowledge, differential equations. Given those equations and the configuration of a system at one particular time, you can calculate what happens at all other times.
That is for what the universe without quantum mechanics is concerned. Add quantum mechanics, and you introduce a random element into some events. Importantly, this randomness in quantum mechanics is irreducible. It is not due to lack of information. In quantum mechanics, some things that happen are just not determined, and nothing you or I or anyone can do will determine them.
Taken together, this means that the part of your future which is not already determined is due to random chance. It therefore makes no sense to say that humans have free will.
I am amazed to see otherwise-intelligent physicists make this silly argument.
Her argument is that the world must be either deterministic or non-deterministic, by the law of the excluded middle. Determinisic is defined as caused by the dynamics of unconscious particles, and non-deterministic is defined as being not determined by anyone's conscious thoughts. So the possibility of free will is defined away in both cases.
The word "random" just means that someone does not know how to predict something. Free will appears to others as randomness, because a choice is being made that others cannot predict. So randomness does not refute free will. Randomness of just one of our descriptive terms for free will.
She says, "randomness in quantum mechanics ... is not due to lack of information." It has indeed been proved that quantum randomness is not due to our lack of info about local hidden variables in a classical theory. But that's all. If you drop the local hidden variable assumption, and assume we live in a non-classical world, then we no longer have any good reason to think that the randomness is due or not due to a lack of information. Quantum mechanics is silent on the issue.
Others try to interpret quantum randomness as a sign of free will, but this is in conflict with evidence. Quantum processes are not influenced by conscious thought. Chaos is deterministic, so it doesn’t help. Goedel’s incompleteness theorem, remarkable as it is, has no relevance for natural laws.
The most common form of denial that I encounter is to insist that reductionism must be wrong. But we have countless experiments that document humans are made of particles, and that these particles obey our equations. This means that also humans, as collections of those particles, obey these equations. If you try to make room for free will by claiming humans obey other equations (or maybe no equation at all), you are implicitly claiming that particle physics is wrong. And in this case, sorry, I cannot take you seriously.
These are the typical objections that I hear, and none of them makes much sense.
It is a little strange to use reductionism to make an argument about the limits of consciousness. Whatever consciousness is, reductionist arguments have told us nothing about it. More broadly, a comment says
"Physics deals with the most fundamental laws of nature, those from which everything else derives." -This is utterly untrue, as well as the statement that differential equations are THE laws of nature. This is most clear in biology. In biology, nothing of importance (nothing general to ALL biological systems) can be derived from physics, or described with any set of differential equations, however complicated they are. Classical mechanics deals with context-independent "particles" obeying some "law" in a defined "boundary" (and initial conditions), whereas all in biology is context-dependent and has no defined boundary condition. This is what Schrodinger, Einstein, von Bertalanffy, Rashevsky, Rosen, Maturana, Kauffman, and many other serious scientists have been pointing out for a while now (that contemporary physics cannot deal with biology).
Saying that "Quantum processes are not influenced by conscious thought" is another verbal slight-of-hand. If you take the reductionist view that all biological processes can be derived from the laws of physics, then consciousness is a quantum process. What else could it be?
When your conscious mind makes a decision, a quantum process in your brain makes a measurement. Outside observers might be able to make some probabilistic predictions, but they will not know your decision for sure until they see it. That is how quantum mechanics works. It is bizarre to see a physicist say anything else.
A physicist in 1900 might well have said that it is hard to imagine a mathematical theory of everything that accommodates free will. Such a person, when confronted with quantum mechanics in 1930, might very well have declared that the theory is perfectly designed to defeat of his arguments.
A comment says
I enjoyed reading this discussion of free will. It left me puzzled, however. I have had the same difficulty when members of my church wrote about free will. (I grew up Catholic, by the way.)
What is free will? I can't find in scriptures. Church sources affirm it, but do not explain clearly what it is. I have concluded that the consequences of good or bad actions are unavoidable, and that it is better to choose the good.
As an answer, I think, this is not completely satisfactory.
You can find a good Catholic explanation in the Catholic Encyclopedia
. And yes, you can find it in Scripture, such as when Jesus said
, "No go and sin no more." Other religions like Islam reject free will.
Some people consider freedom and choice essential to the human spirit. Others are happy to be slaves to their programming.
I have come to the conclusion that a large fraction of people are cognitively unable to question the existence of free will, and there is no argument that can change their mind. Therefore, the purpose of this blogpost is not to convince those who are resistant to rational arguments.
This is like saying most people are unable to cognitively question the claim that we all live in an artificial simulation.
No, it is not hard to understand the possibility of people being entirely pre-programmed. If Bee says that she is unable to make a decision on her own, I will take her word for it. Watching Trump-haters on CNN leads me to believe that they are all pre-programmed.
A reader points out
You conclude there is no free will on the basis that the universe follows differential equations and quantum mechanics, so as I understand it its determinism plus randomness, which cannot add up to free will. Fair enough.
Presumably, we developed a system of differential equations to explain our observations of the universe, and then later developed a theory of quantum mechanics to explain other observations that could not be explained by the former. So an extra system was developed to address observations not covered by the previous system. On the correct basis that free will cannot be explained by these two systems, you reject it. However, what of the alternative possibility that there is yet another system that we have not yet considered that does allow for free will? Quantum mechanics was developed to explain observations that were unexplainable by determinism; we didn't just say that those observations were clearly wrong or somehow explained in a hitherto unknown way by the previous determinism-only paradigm.
I wish to respectfully disagree that "it just can't be" sums up my position. I am pointing out it is in conflict with theories that are built on a huge amount of evidence.
Sure, free will deserves an explanation, but it's not difficult to explain. Free will is a consequence of our inability to predict our own actions with certainty. Ie, your brain arrives at decisions by evaluating the benefits of certain courses of action. You take the one that seems to suit your goals best. But since you are not able to predict what you will do before you actually do it (that being the purpose of the evaluation), you think the decision was "free".
No, this is backwards. Free will is evidenced by the failure of one person to predict the actions of another. I might make prediction of my own actions using the same mental processes that I use to make decisions.
There is no evidence against free will. None at all. She fudges this point by saying that there is evidence for theories that conflict with free will.
By this she means that there is evidence for Newtonian dynamics, and Newtonian dynamics is deterministic. But Newtonian dynamics is not truly deterministic. If you ask for positions of planets, moons, and asteroids a millennium from now, the theory can only make probabilistic predictions. Likewise, you can make probabilistic predictions about what decisions President Trump will make. There is no conflict.
Only philosophers, physicists, and other such people have any trouble with free will. Most people have no trouble understanding that they make decisions. It takes a lot of explanation to see how someone can deny it.
Update: I just spotted a blogger making this comment today
in another context:
As Bertrand Russell said, this is one of those views which are so absurd that only very learned men could possibly adopt them.
Brilliant. Denying free will is another of those views. So is many-worlds, or believing that we all live in a simulation.