Many are of the opinion that there is no metaphysical world beyond the material that we can sense, and that everything is therefore governed by physical cause and effect (some believe that we cannot know if there is anything beyond our world, but that it is possible that something metaphysical exists).

I was wondering if free will had any place in such a purely physical view of the world? If everything is cause and effect, does that mean that we effectively cannot impact what occurs around us and in our heads? That all our actions are the result of electromagnetic waves in our brains?

In short, can free will only exist in a world with metaphysics beyond the tangible realm?

EDIT: My definition of free will is the ability to choose from multiple paths of action in response to one situation.

Regarding the comment about simply responding to an analysis, as computers can do: this does not meet the definition I'm using. In the case of a computer, the reasoning is (as far as I'm aware) constant. What I mean is, given a situation A, a computer will respond with action B, every single time. However, my definition of free will means that given a situation A, an entity knowingly has the choice between doing B, C, or D (or any other number of options), and can choose any one. Presented with the exact same situation, the entity will again have these options, and can easily choose to act differently.

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    People can still talk about free will but in different terms. Free will not as the freedom to go against causal determinism but rather simply to be able to be aware of the options available. Plus, at any rate we still have to act as if we had free will. So there is still a discussion but it gets a bit more complex than merely "can it exist or not".
    – stoicfury
    Commented Jan 27, 2012 at 7:03
  • The definition of free will is, of course, important. If free will is the ability to decide on a course of action based on the input of information, including the loop back input of reflection or reason, then this mechanism is evidently reproduceable, in terms of electronic computers, materially. It is then a matter of extending this mechanism to apply to human senses and brain.
    – leancz
    Commented Jan 27, 2012 at 10:53
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    I spent much of my time pondering this very question over the fall of 2011. The others have answered with what is generally the same conclusion with which I ended up: no, free will is not reconcilable in a purely physical world. This can invoke a great level of despair, so the next question you should ask yourself (and this is another argument entirely) is whether the world is purely physical. It may seem so on the surface, but for example, Kant lays out a convincing argument to the contrary in The Critique of Pure Reason. Commented Jan 30, 2012 at 0:02
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    @Josh1billion - I'm not sure why it "invokes despair" for you. If causal determinism is true, nothing really changes. I still wake up in the morning to go to work, I still love my family, chocolate still tastes delicious. It is of no more consequence to me than the concept of "onomatopoeia" is to a termite.
    – stoicfury
    Commented Feb 1, 2012 at 0:43
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    Individuals will have varying reactions to conclusive knowledge that the world is entirely deterministic and that free will is ultimately an illusion (depending upon how one defines free will). Under certain popular definitions of free will, I suppose the reaction can also depend upon the level of value at which one places freedom and upon how one defines identity. Commented Feb 1, 2012 at 2:09

11 Answers 11


I distinguish between "free will" and "freedom of action".

Free will: A person at a situation A can decide between action B, C, D. He choses B but could have acted differently.

Under the assumption that our decision-making process is not dependent on randomness this is not compatible with a physical world.

All accounts of "I could have acted differently" only work in retrospect. If you are in a situation like A but not A, let's call it situation A', you have gained new knowledge that you never had in a situation A and you were in a different state of mind. Hence making it possible to react differently. Yet still the way you act is a necessity. Deterministic.

Freedom of action: Given a certain situation A a person has multiple options, B, C, D and can decide which to take, without people or circumstances forcing them to take or denying them certain choices.

This is compatible with a physical world as it only takes into account if they can actualize their desire. Viewed in this light, any struggle for freedom is a struggle for freedom of action.

my definition of free will means that given a situation A, an entity knowingly has the choice between doing B, C, or D (or any other number of options), and can choose any one. Presented with the exact same situation, the entity will again have these options, and can easily choose to act differently.

Exactly what I mean by freedom of action.

If you are asked if you want either lemonade or tea to drink, then yes, you have freedom of action to either chose one of them. But given a certain situation at a certain time, you always will come to the same conclusion as your brain works itself to its decision-making process.

Bear in mind that if someone asks you the same question the next day, it is not the same situation anymore. It's merely a situation like A, namely A'.

The one who makes the decision at situation A' is not the same person anymore as they were at situation A. You could think "I drank lemonade yesterday, so I won't today." Or "That tea yesterday was too bitter, I want something sweet."

Yet you can only realize and do what you want but you cannot freely decide what to want.

Of course you could have different desires competing, e.g. "I want to make a diet" and "I want something sweet", yet given which desire is stronger you will act on it accordingly.

given a situation A, a computer will respond with action B, every single time.

Only a primitive program that does not store states will do so. A computer will react differently in situation like A if other dynamic side-conditions are taken into accounts as well.

Yet given the same dynamic side-conditions, the same conclusion will be derived.

The brain is a complex self-programming machine that reprograms itself according to evaluations of past events, and hence will produce different output when presented with similar input. It's what we call learning by experience. (Those experiences could also just be mind-experiments. Just thinking what happens if you jump off a cliff is enough to make you realize that doing so would be unwise.)

If everything is cause and effect, does that mean that we effectively cannot impact what occurs around us and in our heads?

You impact the world around you. And you are impacted by the world. No free will needed.

And what happens in your head is not affected by 'you' but that very process is you. Your very identity.

That all our actions are the result of electromagnetic waves in our brains?

That is too simplistic. The brain gets input, analyses it, abstracts it, categorizes it, conceptionalizes it, puts it in relation with other concepts, and going from there derives or infers plausible causes of action.

It's not just the result of "electromagnetic waves", it's the result of a complex but deterministic (as in: "governed by the laws of physics") process.

It happens that the brain emits electromagnetic waves while doing it, yet I think it is possible though not feasible to build a brain using water pipes.

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    +1 for a very thorough answer. I appreciated your distinction between free will and freedom of action; it made the explanation much more clear.
    – commando
    Commented Jan 29, 2012 at 16:38
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    Good answer and +1, but is there any chance I could persuade you to back up some of this argumentation with citations of some kind?
    – Joseph Weissman
    Commented Jan 29, 2012 at 17:46
  • @JosephWeissman The "freedom of action" and "free will" distinction I first read in Michael Schmidt-Salomon's "Jenseits von Gut und Böse" (AFAIK only avaible in German), which quotes Schopenhauer and Nietzsche quite often.
    – k0pernikus
    Commented Jan 30, 2012 at 19:08
  • > "Under the assumption that our decision-making process is not dependent on randomness this is not compatible with a physical world." Without that assumption it is still not compatible, random isn't free, Two-Face isn't more free for using a coin to make the decisions, in any case he'd be less free for not making the decisions himself.
    – Trylks
    Commented Oct 8, 2013 at 16:29
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    @Futilitarian This debate has made me think of Schopenhauer: goodreads.com/quotes/…
    – k0pernikus
    Commented Aug 4, 2021 at 12:31

From what I have seen, a large portion of the debate over free will arises from unclear conceptions of what one means by the term.

If you do not count your internal state as you but rather as "the situation", and you insist that your free will must be will (neither determined nor random, but selected based on some reason), then you cannot have free will: your reasons depend wholly upon your internal state, which is not really you. (In fact, in this conception, nothing is you, by definition!)

If you allow at least the internal states that correspond to your mind to count as you and not "the situation", then of course you can have free will. Your camera has free will of this sort: it may or may not flash, depending on both whether the flash setting (internal state) and the ambient light levels (external state). (But in this conception, free will is, on its own, not even interesting, because it's so trivially obvious.)

Although one can conceive of free will in more complex ways that either of the two above, either internal state counts as "you" or it does not, so if you are only asking whether it is possible, you need only determine which framework you are operating under.

  • Good answer and +1, but is there any chance I could persuade you to back up some of this argumentation with citations? (You say "from what I have seen" -- where?)
    – Joseph Weissman
    Commented Jan 28, 2012 at 23:15
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    @JosephWeissman - Unfortunately, no, my memory has faded too much given how much free time I have. At least one and probably both of Churchland and Dennett have defined their own terms clearly but have not adequately addressed that others have different definitions, and I can't remember who the couple of (fairly prominent) others were who took the opposite side. Sorry! I would much prefer references (although I think the logic holds together pretty well). Maybe I should delete the "arises from unclear conceptions" sentence, since it's neither referenced nor robustly argued for.
    – Rex Kerr
    Commented Jan 29, 2012 at 0:38
  • I thought it admirably clear.
    – CriglCragl
    Commented May 6, 2020 at 10:12

my definition of free will means that given a situation A, an entity knowingly has the choice between doing B, C, or D (or any other number of options), and can choose any one

Ah, but what do "knowingly" and "choose" mean in a purely physical world?

If you wish to defend a strong materialist view of the world, you have to explain the fact that we have something that looks like mind, which seems to be able to make willful choices; if this is an illusion, it is a pervasive and persistent one.

  • Agreed that an explanation is necessary, but it's relatively easy these days, given that computers can seem to make willful choices (so we already have an existence proof of implementing something qualitatively if not quantitatively the same), and we have no lack of other illusions (e.g. we can't see when we blink or even when we move our eyes, yet we don't notice, among many many others).
    – Rex Kerr
    Commented Jan 30, 2012 at 5:12
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    Computers can make "willful" choices? That seems to me to be begging the question. Commented Jan 30, 2012 at 7:44
  • Computers can be programmed to make choices that do not differ qualitatively from those that humans make, from the perspective of an external observer. (There is a quantitative difference--we are more complex and harder to predict--and we can cheat and know what the computer is attempting to do and interpret its actions accordingly.) It is our internal sense of the nature of our own willful decisions, not how it looks from the outside, that demonstrates a major qualitative difference. (When I choose to do something it does not feel at all like when, for example, I sneeze or blink.)
    – Rex Kerr
    Commented Jan 30, 2012 at 15:20
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    It is our internal sense of the nature of our own willful decisions, not how it looks from the outside, that demonstrates a major qualitative difference. --- And that is precisely what is at stake in the original question here. "Willful" implies a consciousness which is not easily subsumed into a strong materialism. Commented Jan 30, 2012 at 16:15
  • Psychophysics has demonstrated so many dramatic differences between our intuition about how we percieve and understand things things are and how we actually do it that one has very little basis for ascribing deep epistemological significance to any particular experience. In Descartes' time, we had very little else to go on, so it seemed like a good idea. The experiences are still great for motivating questions, and they do end up intuitively providing highly reliable information about the world (in most cases). Our ability to intuitively understand how this happens is woefully bad.
    – Rex Kerr
    Commented Jan 30, 2012 at 16:26

The idea of a purely physical world is not as straightforward as it first appears. If we unpack what we mean by it, a purely physical world is one where everything in it strictly obeys the laws of physics.

At the macroscopic level, this appears deterministic. If you strike one billiard ball with another, the resulting trajectories are completely determined by the speed, force, direction and position of the balls.

At a subatomic level, however, physical laws operate in a way that we understand only statistically and in aggregate. The seeming determinism enters the system when we move to the macroscopic level only because we're dealing with such large numbers of particles that we can round up strong probabilities to certainties.

When dealing with individual particles, however, to the limits of our current understanding, they behave as though they had a "choice". An atom decays at one moment, not another. A single electron goes through one slit or the other. A particle is measured with one spin not another. As far as we know, those eventualities are not determinist, and the very fact that we can observe them at all shows that they are able to have an impact at the macroscopic level under the right circumstances.

  • Even something as large and simple as a billiard ball does not behave in a predictable way. When one strikes another, tiny differences in position, speed, etc can lead to very large differences in trajectory (like the Butterfly Effect) and so this is what makes a horse race. Er, game of billiards. It is not deterministic. It is not random. It is not exactly chaotic either, but that is the closest description we have. "Extremely sensitive to initial conditions." So prediction of something as complex as thought and decisions is right out.
    – user16869
    Commented Mar 1, 2016 at 4:41
  • Quantum indeterminacy, or for that matter classical indeterminacy (sensitivity to initial conditions beyond our ability to measure them) have nothing to do with free will. Particles are unpredictable individually, but follow absolute laws as groups, like following half-life statistics. There is no way to compare their behaviour to choice-making
    – CriglCragl
    Commented Apr 30, 2020 at 21:07

I don't think I would be able to answer with a really strong support, but if your concept of metaphysical free-will is based on repeatibility, then you're basing it on time. If not, there may be no philosophical basis on questioning "I would have been able to act different" because there is no real possibility of having chosen differently, as bound to situation A, you would have chosen action B.

In such a case, still the concept of free-will is not totally incompatible with determinism. Free will may be considered the illusion of choosing C in the situation A where everyone else would have chosen B. And still, when happening a situation identified as A, it is not really A because the person making the choices is not the one that chose in the real original situation. Determinism holds, and still there is some illusion of free will. (Please note that in such an assumption there is no real need of an metaphysical concept of free will, just the illusion based on conceived similarities -- but as perception makes it real, it is real for us.)

Also, all what I said is based on a purely physical and deterministic will, which may not be the real model of the physical world, as there may be a certain amount of chance and indeterminism that is still part of the physical world.

To sum up (and try to make clearer my spaghetti ideas):

  • in a non-deterministic physical world free will is feasible
  • in a deterministic physical world, considering situation A different from situation A' just because its not the same person/time as it is happening, it is still feasible just because our perceptions will make us think we take the choices when situations happen, as we couldn't think the opposite (and, psychologically speaking, I think this would work like some sort of awareness protection mechanism, the illusion of self of which we can't get rid of)
  • in a deterministic physical world, considering situation A equal to situation A' (different person or different time), it is definitely feasible because choices taken can be different

Anyone, feel free to make corrections as you wish. I am in no way an authority on any of the subjects I have mentioned, but this would have been too much for a comment.

  • I thought you were getting at the idea of counterfactuals, which use fixed past events, to make a real imagined probability space in the now, who's structure has real implications for the future. Indeterminacy is a total red-herring, except in relating to limits on what we can know & predict about the world.
    – CriglCragl
    Commented Apr 30, 2020 at 21:13
  • I... actually can't remember the reasoning behind this post. That speaks really poorly of my expression powers hehe -- I hope I have improved since 2012. After re-reading the question and then my answer, I can understand that I'm tackling the problem addressing as no actual "two exact same inputs" to the algorithm. Every instance of "situation A" is then a different one, so yes, I understand how counterfactuals could be involved.
    – Alpha
    Commented May 11, 2020 at 23:38

Peter van Inwagen in his "Metaphysics" (2009) explains point of view that both determinism and indeterminism (which he understands as randomness) are incompatible with free will.

He concludes that as such, free will cannot exist or merely an illusion.

Perhaps the explanation of the fact that both compatibilism and incompatibilism seem to lead to mysteries is simply that the concept of free will is self-contradictory. Perhaps free will is, as the incompatibilists say, incompatible with determinism. But perhaps it is also incompatible with indeterminism, owing to the impossibility of its being up to an agent what the outcome of an indeterministic process will be. If free will is incompatible with both determinism and indeterminism, then, since either determinism or indeterminism has to be true, free will is impossible. And, of course, what is impossible does not exist.

It should be noted though that van Inwagen failed to consider a third option.

A research by Thomas Breuer concluded that neither deterministic, nor indeterministic universally-valid theories are possible. That means that no theory can predict (even probabilistically) the future of a system which contains the observer himself due to self-reference problem.

As such it seems that the free will of at least the observer can be saved while all other people will appear to him as following the laws of deterministic or random theory and as such, not possessing free will.

Particularly, regarding quantum mechanics Breuer proves that a system which includes the observer has states in phase space which are in principle cannot be distinguished by observer himself however good measurement devices he would employ. Yet these states affect the future evolution of the system.

This can be understood as that there is hidden information which real but unreadable by any physical device which affects the future behavior of the observer.

  • If free will doesn't exist or is an illusion then any scientific or logical argument I choose to believe in as useful and clever I do not choose it with my own 'free will'.. Is this paradoxical?
    – user128932
    Commented Jul 15, 2014 at 5:19

Free will and determinism are co-dependent. There's no one without the other.

IMHO There are ambiguities in the question, derived of the lack of concretion about the term "will" and "freedom"

The free will you ask is a physical-laws bound free will. I can have the will to override and revert the energy-conservation principle of physics, but since it is a physical law, there's no way to fulfill this particular deed. We can conceive or imagine a non physical bounded will, although it is out of the question.

In second place, determining one's will is a NP problem, or a non computable one, because one can simply imagine, in any given moment, infinite possibilities (even those physically restricted ones). So, there's a numberability or finitude restriction, a computational restriction if you like, implicit in the definition. Infinity is a non physical concept.

The question is then translated as follows:

Is there an ability to choose between a finite and physical-bounded set of options with freedom?

Lets speak then about freedom. The freedom definition working here is -i guess- that in a given set of options put within a physical environment (let's call it information). Freedom menans then there's no dependence or relation between the previous information that pre-determines the output.

But, how do we know that in any moment an output of a decision system is independent from the environment and the previous finite set of options? We have no way to know it until we compute the solution. And the Turing-Church theorems of undecidability proof that there's no way to predict the output of any given algorithm unless we run it fully.

So, we can only tell whether any given election (choosing or decision) is free or not a posteriori, or so to say: after having executed an decision-taking algorithms, which are intrinsically determined. Freedom lies then in the inherent not-knowing of the answer to that particular decision-taking-assessment problem, a process that is utterly deterministic, rather than the no physical or logical dependence of the output on the premises of election.

In other words, the apparent freedom of any given decision is merely a consequence of the intrinsic uncertainty (undecidability) of any decision taking or assessment algorithm.

So, yes, free-will, as stated before, is a product of the physical and mathematic-logical laws.


The apparent determinism of the Universe emerges as a statistical result of resolution of multiple probabilities. Given a sufficient number of events, the outcome of multiple sets of events at the sub-atomic level, with given probabilities of outcome, will appear consistent and predictable, even if the individual events themselves are not deterministic.

Hence, Free Will could be the ability to change the probabilities of outcomes, while remaining compatible with the apparent deterministic nature of the Universe.

Consciousness, through which free will is exercised, could be a harmonic oscillation of probabilities in that part of space-time that is near to the present but has some liberation from determinism by existing wholly or partly in the near future - where individual event outcomes are not yet determined. By changing the probability of different outcomes of multiple events before individual outcomes have been determined, consciousness can alter the course of events in non-deterministic ways.

Realms of reality

  • I'm interested where this diagram is from? Commented Apr 29, 2020 at 15:50
  • Sorry to disappoint, but it's mine - not from any authoritative source, only to illustrate the idea. I drew it in Powerpoint yesterday.
    – JohnRC
    Commented Apr 30, 2020 at 6:32
  • By way of background, I asked this question 3 months ago.
    – JohnRC
    Commented Apr 30, 2020 at 7:20
  • Ah, nice drawing. Thanks anyway :) Commented Apr 30, 2020 at 10:16
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    Haha I mean nice as in that's a nice concept, and a very good way to represent it. Commented Apr 30, 2020 at 17:15

Free will is not a physical phenomenon, object or event. Therefore it is not reconcilable with a purely physical world.

In such a world there could be no concepts like knowledge, experience, preference, emotion or decision. There could be no thinking, no mental processes at all.

The Universe used to be like that, but it ended when life emerged and organisms started to think.


Two cents.

Libertarian free will mechanism is not that different, conceptually, from a collapse of a present state S which is compatible with a set O of more than one future outcomes, to any one of those outcomes o.

Free choice, in this sense, does not involve any transfer of matter nor energy to happen; only a choice among options which are equally compatible with current state, respecting matter/energy conservation laws, and thus does not violate any physical closure causality. This is strikingly reminiscent of standard interpretations of wavefunction collapse in quantum mechanics which no one claims that it violates physicality or physical closure. Free will need not be reduced to quantum mechanics, but at least conceptually it can be argued that it is not unphysical either for similar reasons.

Furthermore, in this physical universe, there are ways to make sense of me-ness. It can be argued that in any way that I, me, mine can be made sense of in this universe, that same can be used for free will to claim as one's choice. It should be noted that libertarianism claiming that a free choice is not predetermined should not be conflated with out of one's control. First does not mean nor lead to the latter neither is physicality of mechanism of free will harmed.


We can start with an interesting thought experiment: Suppose an alien who has no human attributes and does not know its form of existence comes to Earth, what is human behavior in its eyes?

He will see that most of the material on Earth is ordinary, but there is a portion of it that is a combination of particles with specific shapes. Before they move as a consortium, there are some radio waves within them that engage in high-frequency activity, and sometimes when they are stationary, these radio waves are still active at high frequencies.

So, if this alien had a concept of causality, he would conclude that unless these radio waves enter a low-frequency state (sleep time from a human perspective) during a regular period of time as these particles combine into a stationary state, then the radio waves within these particles will continue to be active at high frequencies. Although this alien may not understand what thinking and reason are, in his view: the radio waves of these particle associations are closely related to their activities, and the frequency of these radio waves will largely determine the trajectory of their movements.

Therefore, when we switch back to the perspective of human rationality to consider our will and actions, we can conclude that the so-called free will has no effect on the particles that make up our body. So at the micro particle level, free will does not exist. No matter how we choose and act, the motion laws and trajectories of microscopic particles remain unchanged. However, as a macroscopic particle consortium, our behavior is truly influenced by our brainwave activity.

You can certainly consider these brainwave activities as a necessary step for particles to engage in collective movement, but at this point, particle movement has two levels: macroscopic collective movement and microscopic independent movement.

I agree with K0pernikus's viewpoint that "experience is a thinking experiment", and all thinking is a virtual experiment. It is precisely because we have learned hypotheses that we have avoided many dangerous events and discovered many additional possibilities in this world of inevitability. However, due to the limitations of rationality, our thinking may not necessarily be entirely positive. We are likely to encounter unnecessary dangers or miss out on opportunities that originally belonged to us due to incorrect thinking.

So, the selection and movement trajectory of a person (or a particle consortium) do not always conform to objective laws, which indicates that as a rational manifestation - the activity of brainwaves - has its spontaneity and plasticity. If it is objectively defined, innate, and unsheatable, then its activity results should fully conform to objective laws.

The above viewpoint is not entirely my original, but rather my reflection extended through studying Kant's philosophy: the reason why human freedom is established is because we have the concept of "should", but what is right and what is not? The answer is unknown and unknowable. However, it is precisely because "should" is unknown and unknowable that talent is able to break free from the constraints of regulations and inevitability.

In summary, my conclusion is that human free will can be compatible with this inevitable physical world, but the prerequisite is that we need to consider this issue from both macro and micro levels.

Furthermore, I would like to refute the viewpoint proposed by k0pernikus from the perspective of causality: humans only have freedom of action, but no free will.

I admit that what everyone wants is determined by causality, as k0pernikus said in his response, "I drank lemon water yesterday, so I didn't drink it today." or "Yesterday's tea was too bitter, I wanted to drink something sweet."

But I don't think this is involuntary and predetermined, because only when we know all the antecedents can we determine the consequences, but events in the entire universe, including human behavior, are the result of the Big Bang. So what are the antecedents of the Big Bang? In other words, what is the primary cause of the universe?

So, no one can fully grasp all the antecedents in the universe, even in theory, because the universe is infinite.

Therefore, we can say that everything in the universe is predetermined due to the existence of causal relationships. But it can also be said that it is precisely because the first cause is unknowable that all events in the entire universe are random, including our human decisions and behaviors.

But we can still determine the authenticity of our free will through our own feelings. The reason is that if we cannot fully grasp the entire causal chain, we can only judge the current facts based on our own feelings.

I would like to emphasize again that it is not that we intentionally ignore causal relationships and use subjective feelings to judge consequences, but rather that when the cause is incomplete, subjective feelings become the most trustworthy thing for us. It can even be extreme to say that any detailed calculation results must be accepted by our subjective feelings in order to become knowledge - they can become your knowledge, but they cannot become my knowledge until my subjective feelings are accepted.

And our subjective feelings and facts when making certain decisions are very clear: I drank lemon water yesterday, so today I chose to drink tea. Of course, there are also times when decisions cannot be made, such as when my leg is pressed down by a giant rock and I want to move but cannot. But this just means that my will has not been realized, does not mean that my will has not been activated, or that it is not free.

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