This question is about the following famous argument (*) against free will:

  1. If determinism is true, the will is not free.

  2. If indeterminism is true, our will would just be a result of chance and we could not be responsible for it.

I'm mostly interested in logically convincing replies to the argument above, regardless how empirically or scientifically implausible they may seem.

If it appeals to something strange (for modern philosophers), like souls, special kinds of causation, ... all the better, because I believe that I may learn the most from it.

(*) One concrete example:

"The argument is exceedingly familiar, and runs as follows. Either determinism is true or it is not. If it is true, then all our chosen actions are uniquely necessitated by prior states of the world, just like every other event. But then it cannot be the case that we could have acted otherwise, since this would require a possibility determinism rules out. Once the initial conditions are set and the laws fixed, causality excludes genuine freedom.

On the other hand, if indeterminism is true, then, though things could have happened otherwise, it is not the case that we could have chosen otherwise, since a merely random event is no kind of free choice. That some events occur causelessly, or are not subject to law, or only to probabilistic law, is not sufficient for those events to be free choices.

Thus one horn of the dilemma represents choices as predetermined happenings in a predictable causal sequence, while the other construes them as inexplicable lurches to which the universe is randomly prone. Neither alternative supplies what the notion of free will requires, and no other alternative suggests itself. Therefore freedom is not possible in any kind of possible world. The concept contains the seeds of its own destruction."

(Colin McGinn: Problems in Philosophy: The Limits of Inquiry, 1993)

  • Since you talk about logic, tell us in what logic you work in.
    – Christina
    Commented Nov 30, 2015 at 7:35
  • 3
    Fallacy of the excluded middle. You're saying that either everything is 100% predetermined, or else it's therefore 100% random. There's an entire spectrum of possibilities that you're not considering, included among them being the one that most closely matches our current understanding of the physical world (i.e. deterministic on the macro scale, and non-deterministic on the micro).
    – aroth
    Commented Nov 30, 2015 at 14:36
  • 3
    Short answer: It's a false dilemma, it assumes that pre-determination and randomness are the only two possible causes for an outcome. Commented Nov 30, 2015 at 16:56
  • 1
    We don't know what 'reality' is, so trying to make absolutely reliable assertions about it seems risky. When we're certain about 'reality', that's when I'll start looking for progress in deciding "free will". Until then, it's all just mental exercise. Commented Nov 30, 2015 at 20:52
  • 1
    Ja'far Sadiq says its in between free will and determination... meaning you have free will within certain restrictions, you don't have infinite options( if that is what you define free will) but you do have more than enough to choose freely
    – Honey
    Commented Nov 30, 2015 at 22:33

6 Answers 6


I suppose what you might be looking for is the idea of the noumenal world, in which pure force of will might exist as a soul or identity of some sort, which somehow links to the real world and can influence it somehow in order to grant will to an individual. Given that such a universe is ultimately unknowable to our limited senses, it can never be discovered by science and could hide behind the pretense of a probabilistic or non-deterministic universe.

Ultimately it comes down to the semantics and concept of 'free' and 'will' being more than just the sum of deterministic or non-deterministic experiences, necessitating something supernatural and beyond the bounds of physics and science in order to remove it from the constraints involved. The alternative is to dismiss the concept altogether for being absurd or untestable and instead question those semantics; an illusion of "free will" may just arise from the ability to be aware of alternate possibilities and the factors involved in a decision rather than some kind of unbridled volition that transcends the laws of physics.

  • This is basically Kant's solution in CPR (the noumenal world is his idea and his solution to the third antinomy which is the apparent contradiction between the physically determined world and the moral requirement for human freedom).
    – virmaior
    Commented Nov 30, 2015 at 14:04
  • @virmaior I believe the concepts of noumenal and noumenon (in contrast with phenomenal and phenomenon) came from Platonic philsophy, but yes, this point of view is Kantian.
    – Danikov
    Commented Nov 30, 2015 at 14:12
  • Yes, exactly, something like that! Are there explanations of the concept of a "noumenal world", so that it isn't just an unanalyzable "philosophical stopgap"... (not Kant's original texts, please, I find those impenetrable)
    – R. Neville
    Commented Dec 1, 2015 at 4:28
  1. If determinism is true, the will is not free.

1.1 Determinism is not true: One could argue for this from a dualist position, that the mind is separate from the body and part of a non-material mental realm that doesn't follow the laws of physics, yet has the power to act on the body in a causal way. DesCartes famously argued for this position, and went so far as to say that the non-material mind acted on the brain via the pineal gland.

1.2 Determinism is true for small systems, but not always true for larger systems. There is no non-material mental realm or supernatural souls or anything, but free-will is an emergent property of the physical brain. Emergence is the idea that a large scale property can appear in an object made entirely of smaller objects, none of which posses that property. For example an elastic piece of rubber is made of a bunch of interacting atoms and sub-atomic particles. Although the elasticity of the rubber is dependent on the way those particles interact, none of the individual protons, neutrons and electrons that make up the rubber exhibit the property of elasticity themselves. Similarly, it has been argued, although I forget the source, that freewill might be such an emergent property of the way proteins, neurons, and chemicals interact in the brain, even though all of those individual components behave in a deterministic way.

2.Determinism is true, but it doesn't preclude freewill: This position is known as compatibilism: The world is deterministic, but free will is still possible, hence free will and determinism are compatible. Defenders of this position, such as Daniel Dennett, argue that we are mistaken in our definition of freewill. Freewill is not the freedom to act against the laws of physics and causality (nobody can defy gravity out of freewill for example), but is instead the freedom to act according to one's own motivations. As long as a system has agency, and has practical freewill, true metaphysical freewill is unnecessary. Once we have adjusted our definition of freewill, then freewill and determinism become compatible.

If indeterminism is true, our will would just be a result of chance and we could not be responsible for it.

This doesn't really change anything. Saying that the world is indeterministic (per quantum mechanics) but that we still have no freewill and all of our actions are just random events amounts to saying that we have no freewill because our minds have to obey the laws of physics. The above refutations (1.1, 1.2 and 2) still hold: Either, per dualism, the mind works outside of physics (1.1), or freewill is an emergent property of what are now random systems (1.2), or freewill is possible despite the mind obeying the laws of physics, per the same reasoning that compatibilists use to reconcile freewill and determinism (Daniel Dennett defends this position as well).

Roger Penrose also gave an argument based on quantum mechanics and neuroscience, which allows for there to be freewill in an otherwise physically causal world.

  • 2
    You say that "to disprove IF A THEN B, you must show either that A is false, or that the relationship doesn't hold". This is wrong. If A is false, then "IF A THEN B" is vacuously true whatever B is. To disprove "IF A THEN B", you must show both that A is true, and that B is false. Commented Nov 30, 2015 at 15:29
  • Thanks for this detailed explanation. The most important point is this: "Either, per dualism, the mind works outside of physics". A defender of the argument in question would say, that this is not enough and use the principle of sufficient reason: The mind (soul) obviously knows something about the world and is influenced by it. If the decision made by the mind isn't determined by this and the psychological state, what is the reason for a certain decision? How could we explain that if we can't give a reason, it doesn't follow that the decision is random?
    – R. Neville
    Commented Nov 30, 2015 at 23:43
  • @PatrickStevens - That doesn't seem right. Or at least, it seems like an oversimplification. Consider a premise like "If I eat breakfast, an asteroid will strike the moon". There's clearly no causative relationship between 'A' and 'B', so how is it reasonable to require someone to show both that 1) I ate breakfast and 2) no asteroids struck the moon in order to disprove that statement? Particularly when both events are fairly commonplace, which may make it exceedingly difficult to point to a case where you have 'A && !B'. But that doesn't make the premise even vacuously true.
    – aroth
    Commented Dec 1, 2015 at 1:24
  • @aroth Then you should probably rephrase as "My eating breakfast will cause an asteroid to strike the moon" :) the only way "If I eat breakfast, then an asteroid will strike the moon" is vacuously true, by the way, is if either you never eat breakfast or if you see an asteroid strike the moon, so perhaps you meant to use "If I don't eat breakfast, then an asteroid will strike the moon"? Commented Dec 1, 2015 at 3:39

Others have already pointed out that this argument begs the question against the possibility of compatibilism, by supposing that freedom must be contra-determinate. Also that it potentially asserts a false dichotomy.

Another point is that McGinn moves from "indeterminism" to "merely random event" and thence to "inexplicable lurches". This move pivots on an equivocation in the meaning of the word "random". In scientific use, randomness relates to stochastic processes: in this sense it is OK to infer random from indeterminate. But in ordinary usage, when we say something is random we mean it is unplanned or unintended. It is only in this sense that we can get from random to inexplicable.

Stochastic processes needn't be unplanned, unintended or inexplicable. In fact, we use (pseudo) random number generators to solve problems such as in Monte Carlo calculations. The results of these calculations are the product of stochastic processes, but they are not inexplicable.

This is an example of a fairly common error in which randomness is reified and treated as a cause.


Another simply flaw in this reasoning is that it provides no proof that those are the only two possibilities.

In order to disprove anything you would need to not only disprove each possibility, but also prove those are the only possibility's. Simply not being able to think of a 3rd isn't enough to exclude it - especially as in this case, given no other information, free will itself could be option C - making those whole argument almost circular by excluding it.

  • What is the third option? FULLY determined or FULLY un-determined are mutually exclusive positions even in a world of mixed random or determined events. Commented Apr 13, 2020 at 19:57

This false choice between absolute, Laplacian determinism and irreducible randomness seems rather crude, hyperbolic, and outdated, even in physics.

There are many compatibilist arguments in the history of philosophy, but even physics today is generally understood as probabilistic, utilizing statistical mechanics with reference to microstates and macrostates. To say that there are limits or "scientific laws" that cannot be violated is not to say that all events can be correlated to determinate causes or outcomes calculated over vast quantities with infinite precision.

Nor can we meaningfully talk about some absolute "indeterminacy" as "true." Even "defining randomness' becomes somewhat paradoxical. The choice is not one that is actually posed by the physical sciences, where it presumably originates. Sorry, I do not know how this might be translated into some logical language. I would simply deny the premises.

  • Regarding the first sentence: "The theory [quantum mechanics] says a lot, but does not really bring us any closer to the secret of the "old one." I, at any rate, am convinced that He does not throw dice." - Albert Einstein (in a letter to Max Born, Dec. 4th, 1926)
    – Philip Klöcking
    Commented Nov 30, 2015 at 16:16
  • True, Einstein never accepted the Copenhagen interpretation and I'm not sure what he thought about Boltzmann's statistical entropy or someone like Prigogine. He was a Spinozian, I believe, and in that sense was a bit "outdated" even in his own later years, though one hesitates to say such thing about Einstein.... who is, after all, Einstein! Commented Nov 30, 2015 at 17:26
  • Einstein was refuted on his statements w/r to QM by Aspects et al experimental confirmation that Bell's inequalities were indeed violated in 1982. There's still a chance that nature is not random, but if it is, then it is not local (Einstein called this spooky action at a distance), which has even more disturbing effects on causality than quantum randomness. Commented Nov 30, 2015 at 23:07

I don't think 'belief in freewill' has any logical connection with anything. I think people get confused because they think, if there's no freewill, everything could be predicted. But in fact the complications are so huge that complete determinism can be true, and yet nobody knows what is determined. Arguments over 'freewill' have occurred at a certain stage in the evolution of life, but there's no connection with what follows. it's all determined, even if it doesn't feel it is.

  • While this dismisses the question, it does so out of hand without sources and without argument (in the philosophical sense). Can you amend with support in both directions?
    – virmaior
    Commented Dec 10, 2015 at 15:03

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