# Does QM allow free will ?

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Does QM allow "free will"?

Some people argue that QM is complete because if there were deterministic hidden variables behind QM, then the determinism would not allow free will.
However, such an argument for completeness of QM is completely meaningless for the following reason: If QM is complete, then fundamental laws of nature are purely probabilistic and physical events are fundamentally random. Fundamental randomness does NOT allow free will. For example, if there are 50:50 chances for two different behaviors of a human, then the human cannot decide to behave allways in the same way.

Thus, everyone who believes in free will should reject completeness of QM!

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There are no deterministic values. Wavefunctions represent the probability ofthings happening, and eigenvalues represent one possible state of the collapsed wavefunction. Thus, no determinism. And a wavefunction with 50:50 values, in its uncollapsed state does occupy both states at once. Like Schrodinger's cat.

But you still have to follow Schrodinger's equation. So, you don't have complete free will.

Fra
I'm not sure about the free will stuff, but I agree ordinary QM is incomplete.

But not for the same reasons that Einstein thought it must be so. My problem is not the "God plays dice" things, my problems lies more in the foundation of probability theory. The postulation of the probability spaces. This is fine from a mathematical point of view, but the connection to reality is another story. I think the probability space itself is only estimated, and thus it is evolving too. However this should be curable, but it will get consequences for the current model.

/Fredrik

Gold Member
There are no deterministic values. Wavefunctions represent the probability ofthings happening, and eigenvalues represent one possible state of the collapsed wavefunction. Thus, no determinism. And a wavefunction with 50:50 values, in its uncollapsed state does occupy both states at once. Like Schrodinger's cat.

Why free will exist ?
free will is just a concept.

Free will is a macroscopic concept, and QM is microscopic. I dont really think that photons and electrons have the concept of free will. I think that we are getting bogged down in philosophical issues.

Gold Member
Free will is a macroscopic concept, and QM is microscopic. I dont really think that photons and electrons have the concept of free will. I think that we are getting bogged down in philosophical issues.
Completely agree.
But do you think that there is a fundamental cut between microscopic and macroscopic? If yes, where exactly this cut is?

Doesnt saying freewill is a macroscopic concept cause more problems? Newtonian physics is completely deterministic as far as I am aware. The reason people have argued that QM allows for freewill is that it seems that only conscious observers can collapse the wavefunction, meaning that conscious observers do indeed affect physical reality.

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Doesnt saying freewill is a macroscopic concept cause more problems? Newtonian physics is completely deterministic as far as I am aware. The reason people have argued that QM allows for freewill is that it seems that only conscious observers can collapse the wavefunction, meaning that conscious observers do indeed affect physical reality.
But consciousness and free will are totally different concepts. Consciousness may exist without free will.

I agree completely but the important part is that consciousness can act on matter in a way. That doesnt necessarily imply freewill but it doesnt exclude it either, especially with the non-deterministic nature of QM. It seems that freewill is possible in QM but difficult to argue for in newtonian physics.

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I agree completely but the important part is that consciousness can act on matter in a way. That doesnt necessarily imply freewill but it doesnt exclude it either, especially with the non-deterministic nature of QM. It seems that freewill is possible in QM but difficult to argue for in newtonian physics.
My point was that in standard QM the physical events are not only non-deterministic. Instead, they are much more than this - they are random. While non-determinism is compatible with free will, randomness is not. That is my main point.

Completely agree.
But do you think that there is a fundamental cut between microscopic and macroscopic? If yes, where exactly this cut is?
I think its where QM becomes to complicated, i.e. on the scale of anything above molecules.

Doesnt saying freewill is a macroscopic concept cause more problems? Newtonian physics is completely deterministic as far as I am aware. The reason people have argued that QM allows for freewill is that it seems that only conscious observers can collapse the wavefunction, meaning that conscious observers do indeed affect physical reality.
Randomness and probability is not an issue in Newtonian mechanics, as relationships are compleely causal. Also, conscioussness isnt really a problem either; a computer isn't conscious, yet it can collapse wavefunctions (if you hook it up to a detector). All that is necessary is a measurement. Observation isnt always the correct word to use.

Thus, everyone who believes in free will should reject completeness of QM!
Isn't the usual concept of free will in contradiction with any physical theory? The theory being deterministic or not, is not a key factor in the paradox, at least not obviously.

I believe that this is a matter where progress will happen through improved understanding of the free will, and not through new physical theories.

Whether a computer can collapse the wavefunction is debatable, as is whether a computer is conscious. I think that observation is the correct word to use, since any physical measurement made without conscious observation would be indistinguishable from normal physical interactions which are constantly happening without any collapse of the wavefunction occuring. Even if the wavefunction collapses in a random (probablistic) fashion, the fact that it collapses is caused directly by conscious observation, meaning that mind does act on matter in some sense. It is not random whether or not the wavefunction collapses or not, only how it collapses. Furthermore, some have argued that the way a wavefunction collapses may not be random but influenced by mind, ie it might be the mechanism by which freewill operates. This is just speculation however and i dont see how it could be easily falsifiable

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TWO big problems here - First;
If QM is complete, then fundamental laws of nature are purely probabilistic and physical events are fundamentally random. Fundamental randomness does NOT allow free will. For example, if there are 50:50 chances for two different behaviors of a human, then the human cannot decide to behave all ways in the same way.
That is upside down, This argument should have QM favoring free will not apposing it – the human can only decide once and will never see the exact same decision to be made again. Both the inputs and the human condition (mood, importance of which of many parameters, etc) all weigh differently on how the final decision is made. A variety of important parameters that cannot be known in advance with any certainty. Certainly not an argument the demands Free Will destroying determinism is true.

And even worse - Second:
Thus, everyone who believes in free will should reject completeness of QM!
What a terrible way to reject or accept the completeness of QM.

In this "Physics" portion of the forum you should more interested in using the Scientific Method. You know, something like Bell Tests or if you can devise one, something better in the form of a real scientific experiment.
After all, almost anyone should doubt QM just based on Commons Sense (At least a commonsense not educated with the experience of using QM in 70 years of scientific technological advancements far exceeding the advancements of 2 millennium prior years). Only using an Ordinary Common Sense would reject QM simply based on the Weirdness of it, without debating “Free Will”.

If you do not want to expand the Common Sense used on issues like this, with information gained from real experience and applying the scientific method – shouldn’t you have this issue moved to the Philosophy Forum instead?

vanesch
Staff Emeritus
Gold Member
The question of free will is a completely philosophical issue and has not much to do with a physical model and whether that physical model is "random" or "deterministic". A deterministic model simply means that if we were to know up to infinite precision the "state of nature" at a certain moment, then we can know the state of nature in the future. A random model means that even if we know the precise state of nature at a certain moment, we can only describe the future by the means of probability distributions. So the nature of a model to be deterministic or probabilistic is only a way to describe how we can KNOW the future.

Now, think of "nature" as a big bag of events, distributed in spacetime. That means that anything in the future is "in that bag", and hence is somehow "determined". There is an event in the bag that tomorrow, you'll pick chocolate pudding for dessert, and not fruit salad. It simply means that tomorrow you will indeed pick chocolate pudding. In a deterministic model, there is in principle a way to find that out if I'd know all the events on the "today" hyperplane, while in a probabilistic theory, I can only find a probability distribution which assigns a certain probability to the event "you will eat chocolate pudding" tomorrow and another probability to "you'll take fruit salad" (which you eventually won't). Does this mean that the fact that you will "freely decide to eat chocolate pudding" is not free in one case, or in another ? Not really. The only thing we're talking about is our ability to KNOW what you WILL DECIDE, given all events on the "today" hyperplane. It doesn't change anything that you will decide to go for the chocolate pudding tomorrow! We're only talking about our ability to link events today and that event tomorrow.

In order to illustrate this, let's look to the past instead of the future. Let's look at Julius Caesar, and his getting over the Rubicon river. We know that he did. Does the fact that we KNOW that he'll cross the Rubicon (by looking at all events today, and especially events related to history books) on the "today" hyperplane mean that Caesar didn't have any free will at that moment ? Because that event in the past cannot be changed into "he'll not cross the Rubicon", and is strictly determined by events in our "today" hyperplane ?
Would he have had more or less "free will" if our historical record would be less clear, and we'd have to assign a certain probability for him to have crossed the Rubicon and another probability if not ?

nrqed
Homework Helper
Gold Member
Some people argue that QM is complete because if there were deterministic hidden variables behind QM, then the determinism would not allow free will.
However, such an argument for completeness of QM is completely meaningless for the following reason: If QM is complete, then fundamental laws of nature are purely probabilistic and physical events are fundamentally random. Fundamental randomness does NOT allow free will. For example, if there are 50:50 chances for two different behaviors of a human, then the human cannot decide to behave allways in the same way.

Thus, everyone who believes in free will should reject completeness of QM!

I agree 100% with you.

This is kind of eerie...I made exactly the same point to a friend of mine about a year ago!

Clearly, there is no place for free will in the context of classical mechanics. However, I have read statements sometimes to the effect that free will is actually "salvaged" by quantum mechanics. However, just a few seconds of thought makes it clear that this is not true at all!! A random quantum mechanical process does not allow free will more than a completely deterministic (classical) process. In both cases, free will has no room!!

It seems to me that the very idea of free will can have no explanation within a scientific theory. Because the very idea of free will involves an effect without a cause. So it seems to me that either free will is an illusion or if it is real, there *must* be something beyond science that is at work.

My personal opinion is that free will is simply an illusion created by our mind.

I am no expert in mind and brain studies, but there are clearly situations in which our brain perceive some external stimulus and reacts in a way that gives the impression that free will is not involved...we simply "react" "instinctively" to something and we do it so quickly that we say "I did not think, I just did it". I have read about two pathways of decision making in the brain, and one would go through a shorter route (which involved avoiding the neocortex or something like that... I don't remember but I could dig it up). It was theorized that this path involved reactions in which we don't consciously have the impression that free will is involved. My point is of course that even in the case of the other path, free will is not really present at all, but the illusion of it is generated.

My point is that I think that it's not only in those type of situations that free will is not involved. I believe that in *all* situations, free will is an illusion.
Except that in most situations, the brain creates an illusion of free will. The questions is obviously why we would have evolved this need. I have some ideas about this but I am sure nobody will be interested in my ramblings so I will stop!

Patrick

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I agree 100% with you.

This is kind of errie...I made exactly the same point to a friend of mine about a year ago!

Clearly, there is no place for free will in the context of classical mechanics. However, I have read statements sometimes to the effect that free will is actually "salvaged" by quantum mechanics. However, just a few seconds of thoughts makes it clear that this i snot true at all!! A random quantum mechanical process does not allow free will more than a completely deterministic (classical) process. In both cases, free will has no room!!

It seems to me that the very idea of free will can have no explanation within a scientific theory. Because the very idea of free will involves a cause without an effect. So it seems to me that either free will is an illusion or if it is real, there *must* be something beyond science that is at work.

My personal opinion is that free will is simply an illusion created by our mind.

I am no expert in mind and brain studies, but there are clearly situations in which our brain perceive some external stimulus and reacts in a way that gives the impression that free will is not involved...we simply "react" "instinctively" to something and we do it so quickly that we say "I did not think, I just did it". I have read about two pathways of decision making in the brain, and one would go through a shorter route (which involved avoiding the neocortex or something like that... I don't remember but I could dig it up). It was theorized that this path involved reactions in which we don't consciously have the impression that free will is involved. My point is of course that even in the case of the other path, free will is not really present at all, but the illusion of it is generated.

My point is that I think that it's not only in those type of situations that free will is not involved. I believe that in *all* situations, free will is an illusion.
Except that in most situations, the brain creates an illusion of free will. The questions is obviously why we would have evolved this need. I have some ideas about this but I am sure nobody will be interested in my ramblings so I will stop!

Patrick

Clearly, there is no place for free will in the context of classical mechanics.
Once again, I do not see any Scientific Method or justification behind this conclusion ether.

If Classical Mechanics was deterministic we should have a definite complete and none generalized solution to the three body orbital problem. Even if there were, in a realistic world with unknown external N bodies introduced from outside a giving orbital system, I do not believe there is any scientific justification for declaring any theory deterministic.

I am convinced that whether or not this thread winds up being moved has not been pre-determined, but will be up to someone’s “Free Will”.

i believe that the world behaves deterministically... all the way. There is 1 or 2 fundamental particles, and a single law that governs the interaction between them. Under this view, given an initial arrangement of the particles, entire future is determined... So there is only one single destiny, and only one way things can happen... After all ... what is free will? The ability to choose? Choice is a result of electrical impulses in your brain, which follow the laws of physics... so faced with a decision, you should always respond in exactly same way, and it was all predetermined in the big bang...

Fra
Now, think of "nature" as a big bag of events, distributed in spacetime. That means that anything in the future is "in that bag", and hence is somehow "determined".
Not that I find the link to fre will very interesting but I'd like to see that bag in it's entitry on my desk for analysis

This is IMO at the root of the probability interpretation, and IMO it's a serious issue and one of the weak points of QM in my eyes.

The problem is that this bag is not totally determined from experiment, in the axiomatic treatment it's imagined to have some existence without beeing explicity "observed". This is inconsistent with the ideal that everything should be measurable or follow from experiment, directly or indirectly. It is however true that this bag can be indirectly inferred from experiment, but the we get a statistical bayesian estimate of the bag only. Thus the probability space that is used for founding QM, is at best identified to a bayesian-like estimate over the space of probability spaces (and even that is fuzzy because by the some token the space of spaces is itself not given).

So I'd say that quantum mechanics is complete only to a certain level of estimated confidence. Sufficiently confidence to provide a basis for fairly successful (but strictly speaking speculative) predictions, but to postulate this is speculative from my fundamental philosophical standpoint, except for practical and "effective" purposes.

The standard motivation about statistical ensembles is easy to buy, but IMO it does not stand up suffciently well to an analysis of the line of reasoning, and in the quest for bigger theories I don't hesitate to throw these postulates back where they came from.

/Fredrik

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vanesch
Staff Emeritus
Gold Member
Once again, I do not see any Scientific Method or justification behind this conclusion ether.
The point is that the question is not open to scientific inquiry via the scientific method - that's why I said that it was a purely philosophical issue.

Indeed, how do you discriminate experimentally between "entity A (say, a person) will decide by free will, X and not Y" on one hand, and "entity A has no free will, but will decide X, but will have the illusion that he decided that" ?

You can only observe that entity A picked "decision X", and declared that he freely decided to pick X. Whether an "alternative" Y was potentially possible, but it wasn't picked, or whether the alternative Y wasn't really a genuine alternative and only X remained, is unexplorable by the scientific method. We can only observe that it didn't happen, and that X happened. In as much as we are lacking information and still don't know that Y couldn't really happen, or in as much that it "could actually happen but didn't", we have no way to discriminate.

nrqed