Quantum mechanics and the return of free will

Many worlds make free will possible

The common definition of free will often has problems when relating to desire and power to choose. An alternative definition that ties free will to different outcomes for life despite one's past is supported by the probabilistic nature of quantum physics. This definition is compatible with the Many Worlds Interpretation of quantum physics, which refutes the conclusion that randomness does not imply free will, writes Tim Andersen.


Free will is one of those things where people tend to be very attached to its being true or false and yet most people implicitly treat it as true. Consider that we hold people accountable for their actions as if they decided to carry out those actions of their own free will. We reward people for their successes and discoveries likewise. If Albert Einstein didn’t really make his discoveries but it was, instead, inevitable that his brain would do so, does he really deserve his Nobel Prize?

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Some argue that we should accept that free will is a myth and change our society accordingly. Our justice system (especially in the United States) is heavily invested in the free will hypothesis. We punish people for crimes. We do no treat them like broken machines that need to be fixed. Other nations like Norway, however, take exactly this approach.

Many physicists believe that free will in incompatible with modern physics.

The argument goes like this:

(1) Classical (non-quantum) mechanics is deterministic. Given any initial conditions to a classical system, and the entire future and past state of the system can be determined. There is no free will in determinism.

(2) Quantum mechanics allows for randomness in the outcomes of experiments, but we have no control over those outcomes. There is no free will in randomness.

(3) Human will is a product of the brain which is a physical object. All physical objects are subject to physics and the sum total of physics is contained in classical and quantum mechanics (technically, classical is an approximation of quantum).

Ergo, humans have no free will. Our brains are simply carrying out a program that, while appearing to be making free choices, is in fact just a very complex algorithm.


As Schopenhauer said, ‘Man can will what he wants but cannot will what he wills.’


The logic seems sound and in any philosophical discourse we need to look at the logic and decide (whether freely or not). There are quite a few ways to counter this argument. The first is to object to #3. This is the approach many religions take. Human will is not necessarily reducible to physical causation. Therefore, it is beyond physical law. The brain simply interacts with the will and carries out its commands.

Another is to question the reductionist assumption of the conclusion, i.e., that everything is reducible to the properties of its constituent parts, no matter how complex. If the individual parts are deterministic, so must the whole. Science has not proven that yet. Perhaps if we could model a human brain in a computer in its entirety, we might know better.

Another approach is to question what the scientist means by free will. Most scientists aren’t philosophers and don’t necessarily define their philosophical terms as clearly as their scientific ones. The common definition of free will is that it is the freedom to choose, the ability to decide to choose or do otherwise, to be the source of one’s actions. Philosophers largely tie free will to the concept of moral responsibility. Am I morally responsible for my actions?

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To put is precisely, an agent S is morally accountable for performing an action ϕ =df. S deserves praise if ϕ goes beyond what can be reasonably expected of S and S deserves blame if ϕ is morally wrong. The key then is whether an agent has the ability or power to do otherwise.

Now, what does it mean to have the ability to choose or do otherwise? It can’t simply mean to have the power because one must have both the power and the desire. But what if one does not have the power to change what one desires? Then you are stuck with no free will or only a pseudo-free will in which you can change your actions but not your desires.

As Schopenhauer said, ‘Man can will what he wants but cannot will what he wills.’ Consider, if I have a choice to practice my cello or lift weights, I choose to practice my cello. Now, I seem to have had the power to choose to lift weights but I did not have the desire to do so. Did I have the power to desire differently?

From the argument of physics, the brain’s desires are either fixed results of classical laws or random results of quantum effects. A random quantum fluctuation creates voltage bias in one of my neurons which cascades to other neurons and suddenly I want to lift weights. According to the physicist, I did not choose. It just appeared as if I did. And certainly if I had chosen differently I would have done differently, and yet in reality quantum physics chose for me by rolling a cosmic die.


You have to see free will as having the power to have different outcomes for your life despite your past.


This kind of free will definition, which is the one most people think of and the one that most scientists seem to assume, has a lot of problems. It’s hard to even understand what we really mean by freedom because it gets all muddled with desire.

Without a good definition, it is impossible to argue that something exists or not. Another definition of free will avoids this problem and throws a monkey wrench into the scientist on the street’s knee-jerk attitude that free will is impossible in a quantum world.

This alternative is called the categorical analysis and is stated as follows: An agent S has the ability to choose or do otherwise than ϕ at time t if and only if it was possible, holding fixed everything up to t, that S choose or do otherwise than ϕ at t.

What this means is that we have to take into account the state of the agent up until the time the choice is made and given that state ask if there is a possible world where the agent makes a choice other than the one he or she made. That, then, is what freedom of choice is.

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Oxford physicist David Deutsch favours this definition of free will because it is compatible with his Many Worlds Interpretation (MWI) of quantum physics. But even if you don’t accept MWI, what it says is that there are probable states that have the same past up until a point t and then a choice is made and a non-deterministic path is followed. It doesn’t matter if those paths are all “real worlds” as Deutsch believes. What matters is that they have different futures, and all interpretations of quantum physics as-is support this idea.

If that is true, and this is the most important point, then you can say that freedom of choice exists because the agent made different choices in different probable realities. Thus, the agent had the power to choose and exercised it.

This definition of free will is interesting from a physics perspective because it is not true in a classical, deterministic world in which all pasts have the same future, but it is true in a quantum world where all pasts do not share the same future. Thus, it refutes the conclusion from #2 above that randomness does not imply free will. It only does so if you define free will in the way that people commonly understand it which is, frankly, not a defensible definition.

Rather, you have to see free will as having the power to have different outcomes for your life despite your past. Whether you can affect those outcomes by changing your actions or desires is a meaningless statement.


Freedom of choice exists because the agent made different choices in different probable realities.


Thus if I made the choice to practice in 60% of quantum futures and lift weights in 40%, then that proves I had the power to do otherwise. If I practiced in 100% of futures, then I did not have that power. Whether science can prove this is an open question, but it does not require any modification to quantum theory. Indeed, some modifications attempt to remove this possibility, incorrectly I believe.

While it may seem that this is sleight of hand in changing definitions, it is in reality making the definition of free will precise by saying that it is exactly the power to do otherwise. This is evidenced by quantum physics, i.e., because more than one outcome of a choice can occur from a single state of the universe, an agent does have “the power to do otherwise” which is what free will is.

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Tomas Schutz 1 August 2023

This article still doesn't address origin of your desires and autonomy! I found all previous articles on Free Will from IAI erroneous and give closest word i could find argument which is modal fallacy (when validity of an argument is judged without omitting its premises or conlusions). I also find most scientists/philosophers really having no idea about Free Will and give logically fallacious arguments... Which is most important thing! Nietzsche said to change one's fate you would have to change everything that was before (whole history), as everything is one whole. And called causa sui rape of logic and nonsense from this reason... Note: there is 2 interpretations of causa sui 1. Metaphysical: that one causes itself into being (this is what Galen Strawson argues for, which Nietzsche called rape of logic), even this has 2 sub-types: a) one can do everything metaphysically possible which even physical laws don't allow, like flying yourself by thinking it, which is nonsense! And b) one would have to cause origin of his desires, e.g. cause itself to existence, yet preceding its own existence, which seems logically impossible! Therefore we don't necessarily come into paradox, but this is logical proof that it is impossible to do so! But we also don't know nature of consciousness and don't have definition of will, so it may not encompass all possibilities there are i.e. logical fallacy... 2. Causa Sui is something of which action originated, and origin of an action cannot be traced to anything but itself, which doesn't seem the case, as everything is in relation! There is argument that Nietzsche misunderstand this interpretation of Causa Sui, but I don't think so, because there is no account of this being possible: maverickph ilosopher.typepad. com/maverick_philosopher/2009/05/nietzsche-on-causa-sui-and-free-will. html I don't understand why it would be so easy to figure out, life without free will turns into hell, even true freedom is in power and in moment (flow) - Nietzsche. Hopefully it is unprovable, so there are ppl which will always believe it... Truth != good... Free will is absurd, there is just will and even that may be only epiphenomenon. We have no definition of will... While I knew that, it is absurd! Because either imagination, or less language which describes these images can describe reality as it is! So if we had free will, we couldn't even know it and what is more absurd it would appear to us that we don't have it! Could one become unfree, from his own free will? OK where i was, i can't prove it is illusion, but biggest geniuses in history thought so... Most ppl don't want to believe it and most ppl even high IQ (it doesn't protect vs biases and dysrationalia) want to believe it, because otherwise they could never feel sense of achievement and pleasure if they succeed and would become depressed, life strives to hide truths which are not beneficial for survival... As Nietzsche said also, there is empirical evidence it is the case! So we cannot even prove/disprove it like with anything, but it is still useful to research all avenues... My problem with desires, is even if future is open to any decision, where it would come from. It is not like you can make any decision at any exact moment, e.g. if you don't know any better, we are rationally bounded, act on imperfect knowledge. Your self is not exempt from your environment which no one chooses! Like what you had parents, it establishes your personality and values for most ppl and you didn't choose these either... Also if we had free will, which ones would be freeer? How it would be determined where other ppl can impend our free will, which will prevail? Also it was proven that ppl, give false reasons for doing something retrospectively, after they are asked later and it is not only snap second decisions (reflexes)! How can you have free will, if you don't even know true reasons for why you did something? And even if we use philosophical concept of character development, at time in past when you make some decisions you didn't know to which it will lead in future, but we can make case, that if ppl know ahead what it will lead to if they make these decisions vs those to form their character they would choose otherwise... There is probably only will and again even that might be just epiphenomena, it is really depressing yeah! But i am sick and i was too deep in abyss, so i need to just know, otherwise i wouldn't want to know this... Like multitude of forces, even intelligence might be illusion, of what we think it is... What if i am boltzman brain? Most of these theories come short I claim because 99.999% are not even strong enough to see the truth... “The strength of a person's spirit would then be measured by how much 'truth' he could tolerate, or more precisely, to what extent he needs to have it diluted, disguised, sweetened, muted, falsified.”. Even this might be too much truth... But what is everything is god and i am all of this? DOes it really matter? It didn't matter to me when i was in moment, that fw is illusion! When i was interacting with other ppl and i felt sublime! As Nietzsche said about antromorphisms, metonyms and ego... We need to do away with bad language... We just basically started to study this... That we care about free will is sickness in the first place, i am not fully healed yet, so i can't explain this to you but read Beyond Good and Evil!

And one quote for the end :D

“Anyone who manages to experience the history of humanity as a whole as his own history will feel in an enormously generalized way all the grief of an invalid who thinks of health, of an old man who thinks of the dream of his youth, of a lover deprived of his beloved, of the martyr whose ideal is perishing, of the hero on the evening after a battle that has decided nothing but brought him wounds and the loss of his friend. But if one endured, if one could endure this immense sum of grief of all kinds while yet being the hero who, as the second day of battle breaks, welcomes the dawn and his fortune, being a person whose horizon encompasses thousands of years, past and future, being the heir of all the nobility of all past spirit - an heir with a sense of obligation, the most aristocratic of old nobles and at the same time the first of a new nobility - the like of which no age has yet seen or dreamed of; if one could burden one’s soul with all of this - the oldest, the newest, losses, hopes, conquests, and the victories of humanity; if one could finally contain all this in one soul and crowd it into a single feeling - this would surely have to result in a happiness that humanity has not known so far: the happiness of a god full of power and love, full of tears and laughter, a happiness that, like the sun in the evening, continually bestows its inexhaustible riches, pouring them into the sea, feeling richest, as the sun does, only when even the poorest fishermen is still rowing with golden oars! This godlike feeling would then be called - humaneness.”

Mahmoud Yacout 20 May 2023

The author assumes that desiring is the same as choosing, that I find a flawed assumption. Assuming that a desire emerges out of some random electrical activity in the brain, so here we are, doomed to do something we didn't choose because of the randomness of the universe. We all desire lots and lots of things, but doing or choosing to follow a desire is something else in my opinion. It is just not that simple, unfortunately. We all have these moments in our lives where we are faced with a choice, whether a hard or an easy one, and sometimes we choose something that's not in accordance with what we desire. Other times we choose something and have regrets afterwards, and then get back to the starting point and choose a different path. I am not giving here a final answer to the debate of free will, but just saying that abstracting the human mind in the way the author did is not right.
The author also refers to the non deterministic nature of the universe, viewed from the perspective of quantum mechanics, as being random, while it could also be viewed as a universe with multiple probabilities or a "multiple choice" universe. Or may be our brains exploit this randomness to create a free or semifree Will!

Michael Walker 12 May 2023

Interesting indeed.