So I'm confused on how this is possible.

  1. If determinism is true freewill does not exist:

If determinism is true, then every event has a cause, and every cause has a unique effect. If every event has a cause, and every cause has a unique effect, then our actions are also determined. If our actions are determined, then we do not have free will, because free will requires us to be able to choose between different possible courses of action.

  1. If the time evolution is probabilistic then freewill cannot exist:

The argument that probabilistic time evolution undermines free will goes as follows:

If our actions are determined by the laws of physics, and the laws of physics are probabilistic, then our actions are also probabilistic. If our actions are probabilistic, then we do not have free will, because free will requires us to be able to choose between different possible courses of action.

I find it strange that the phenomena of determinism - D's validity actually informs us on freewill. Because if D is true I conclude freewill is false. But if D is not true I conclude freewill is false.

Naively I'd just conclude the status of D does not inform us about freewill but that's confusing. What logical error am I making?

  • 1
    Determinism is a broad concept: thus it is hard to say that it is a true theory or not. Free will exists. Commented Oct 24, 2023 at 18:05
  • Free will is the basic assumption supporting the idea of individual responsibility. Commented Oct 24, 2023 at 18:11
  • 1
    Your argument does not have the form "if D then ~F; if ~D then ~F"; it has the form "If D then ~F; if E then ~F" where E is not the same as ~D. So even if one accepts your argument, it doesn't prove what you intend it do. Commented Oct 24, 2023 at 19:42
  • The view that determinism is incompatible with free will is called hard determinism. The majority position is compatibilism, the opposite view. "If our actions are probabilistic, then we do not have free will" does not follow even if free will requires us to be able to choose between alternatives. We may be able to so choose, but also have what is called "propensities" to choose a certain way, which lead to a probabilistic distribution of choices in the long run.
    – Conifold
    Commented Oct 24, 2023 at 23:24
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    What you are asking about is libertarian free will, the idea that we can somehow make decisions independently of the laws of physics. This is not the definition of free will knowledgeable people go with, as conifold said. In the context of libertarian free will, though, you are onto something: determinism is irrelevant as the real hard problem of libertarian free will is not if we could have acted otherwise that we did, but how does our "will" (whatever that is...) modify causality in order to inform our body's actions.
    – armand
    Commented Oct 25, 2023 at 0:11

6 Answers 6


I'll address your question on both logical and semantic levels.

Logical discussion

Your confusion about "informative" is due to your inconsistent definition of "informative":

You first say

If determinism is true freewill does not exist

From which you conclude

D's validity actually informs us on freewill

If we let I(x,y) represent the formula "x is informative of y" then your conclusion is equivalent to:

D ⇒ ¬ F ⇒ I(D,F)

Then you say you

Because if D is true I conclude freewill is false. But if D is not true I conclude freewill is false.[...]Naively I'd just conclude the status of D does not inform us about freewill

Now, you are saying:

¬(D ⇒ ¬F ∧ ¬ D ⇒ ¬F) ⇒ I(D,F)

Which is a stronger condition then your first one.

I think this second definition makes more sense for the idea of "informative of" than the simpler "If A then B therefore A informs us of B".

But, there is also a semantic/conceptual issue you may want to address

Semantic discussion

First, let's clarify what we mean by "free will" - even nailing this down has led to a lively (and still ongoing) debate amongst philosophers.

There are different ways to classify the views on free will, but for this question we can think of free will in two broad senses:

Causal viewpoints (How did the agent decide?)

Also called "Libertarian" or "counter-causal" free will, these viewpoints define "free" as in "free from causality". They argue that our actions are "self caused" vs the outcome of physical laws (deterministic or statistical). These views make a distinction between "randomness" and "choice" for an agent. The spontaneous fission of a uranium atom may be "self caused" in the sense that it wasn't determined by prior events, but it's hard to see how an agent randomly choosing things also doesn't rob us of agency.

Note that it is insufficient to characterize this kind of freedom as "Could have chosen otherwise", or something like "Agent S decides to perform action X with the world in state W; however, there are possible worlds where S doesn't perform action X under the same state of W." Both of these conditions are met merely by allowing the agent to act randomly.

Libertarian free will has the challenge of explaining exactly what this "third mode" of action is if it's neither deterministic nor random.

Say I decide to vote for Candidate A because I think they are more likeable. Assume I have counter-causal free will. One could ask then what made this choice free? I presumably acted logically in accordance with my highest-weighted dimension in a candidate (likability). But why did likability rise tot he top as the deciding factor? How did it win out over other dimensions like tax policy, leadership skills, fashion sense?

Well, I freely chose to emphasize likability, and so if Candidate A ends up being a bad leader I am partly responsible for putting them in office due to not choosing to consider a more relevant dimension. It's hard to see how this kind of choice is anything but another instance of determinism or randomness. And so on in infinite regress.

Source viewpoints (Where did the decision originate?)

For these views, an agent is "free" in the sense of being "free from external coercion" (e.g., being held at gunpoint or being controlled by some futuristic technology). So I am free insofar as I can act in alignment with my intrinsic priorities.

Simple example being "I like to have coffee in the morning, so I decide to make a cup of coffee." In this case I am acting with "free will" in this interpretation. It doesn't get into why I like coffee in the morning or if I could have instead chosen to drink tea. I acted in accordance with my desires/goals and hence made a choice freely.

Of course, I could change my preference to tea, either due to some random event in my brain or due to some other chain of causes (e.g., I found a new flavor of tea that is even more enjoyable than coffee).

A challenge for this view is the blurry boundaries around "coerced/forced" since we are not closed systems, but constantly interacting with the world.

Another challenge here is more about moral implications: if we don't choose (in the Libertarian sense) to want what we want, are we really accountable for our actions?

Now on to your argument :)

Is free will independent of determinism?

I see two implicit assumptions in your argument:

1: Free will is non-random and uncaused (Libertarian free will)

2: There can be only two modes of causation in the world: deterministic or random (physicalism/naturalism)

As you can see, the seeds of free will's destruction are present in the above, since (2) rules out the needed ontological space for (1) to be true. So Free will is false regardless of whether we act deterministically or non-deterministically (which here is equivalent to acting randomly).

Under these assumptions, you rightly conclude that determinism is not informative of free will because we've already assumed free will requires non-deterministic, non-random causation self-action.

If we instead take the source-based view of free will, then we will also find that determinism is uninformative of free will because regardless of how we came to our decisions, if we made them without coercion (freely in the source sense) then we are exercising our free will.

If we keep free will as "Libertarian" free will and allow for the possibility of causes that are neither deterministically caused themselves nor random (let's call it an L cause - for Libertarian), then determinism becomes informative:

(1) (L ∨ D) ∧ ¬(L ∧ D)
(2) D ⇒ ¬F
(3) L ⇒ F
(4) if ¬ D:
 (4.1) L (1,4)
 (4.2) F (3,4.1)
(5) if D:
 (5.1) ¬ L (1,5)
 (5.2) ¬ F (3,5.1)

Then, with our definition:

¬(D ⇒ ¬F ∧ ¬ D ⇒ ¬F) ⇒ I(D,F)

We see that indeed I(D,F)


A world might be non-deterministic because at least some of its fundamental laws are probabilistic

So it is indeed an issue. The incompatabilist response I - FWIW - find fairly irrelevant

Some incompatibilists have responded to the “determined or random” dilemma in a different way: by appealing to the idea of probabilistic causation (Kane 1996, 1999, 2008, 2011a). If our choices are events which have probabilistic causes (e.g., our beliefs, desires, and other reasons for acting), then it no longer seems plausible to say that we have no control over them. We make choices for reasons, and our reasons cause our choices, albeit indeterministically. Kane’s reply may go some way towards avoiding the second (no control) horn of the dilemma. But it doesn’t avoid the first horn. If our choices are caused by our reasons, then our choices are not the first causes of our actions. And our reasons are presumably caused, either deterministically or probabilistically, so they are not the first causes of our actions either. But then our actions are ultimately caused by earlier events over which we have no control and we are not the ultimate sources of our actions.

Anyway, in a hard determinist universe, any will to do otherwise is impossible.

If the agent’s desire to achieve that end does not actually play a role in causing the agent to take the means to that end, then all the states of affairs in which it does play such a role are counterfactual states of affairs... According to hard determinism, such counterfactual states of affairs are physically impossible—that is, all counterfactual states of affairs are such that there was never a point in time at which it was physically possible for them to be instantiated in the actual world.


So supposing that every probabalistic law ends up being explicable without probability (i.e. in a hard determinst universe), then a counterfactual analysis would mean any other behaviour than the one we do is impossible, and it doesn't matter if our psychology is probabilistic, and probabilistic reasoning alone doesn't suffice to allow for free will (the linked to article, which I barely read much of, argues for virtue ethics in response)

  • anyway, i'm just trying to add to the conversation and make something of my comment. i hope it covered enough ground to be useful in some sense
    – user67675
    Commented Oct 24, 2023 at 17:43
  • 1
    the incompatibilist response you quote is basically quantum mysticism, i.e. "we don't understand it, but let's say it's quantic and nobody will dare to argue". But as long as nobody can provide an explanation for how our thoughts can influence the probability of our physical actions, it's nothing but word salad, as you correctly point.
    – armand
    Commented Oct 25, 2023 at 0:19

You seem to have concluded that D is irrelevant on the grounds that F is ruled out whether D is true or not. That's a mistake. F is ruled out if not D only if P. It's rather like the following...

  1. If it rains I will wear my coat tomorrow.
  2. If it doesn't rain I will wear my coat tomorrow.

You can conclude from 1) and 2) that whether it rains is irrelevant to whether I will wear my coat tomorrow.

Contrast that with:

  1. If it rains, I will wear my coat tomorrow.
  2. If it doesn't rain, but it is cold, I will wear my coat tomorrow.

You cannot conclude from 3) and 4) that whether it rains is irrelevant.

  • Ah can you do a similar analysis for the determinism argument? Commented Oct 24, 2023 at 21:03
  • 1) If D is true F is false. 2) If D is false F is false. You can conclude from 1) and 2) that D is irrelevant, Commented Oct 24, 2023 at 21:15
  • However, 3) If D is true, F is false. 4) If D is false, F might be true, depending on whether P is true. You cannot conclude from 3) and 4) that D is irrelevant. That's because it is possible for both D and P to be false. Commented Oct 24, 2023 at 21:31

The question is asked from a monist physical reductionist perspective. Meaning it assumes our mind states can in theory be reduced to physical states, and so our minds ability is bound by the laws of physics. This is possibly also the currently most popular stance in the western world (it does not defy science nor requires unscientific beliefs).

Under those assumptions, philosophic writing offer two positions: compatibilism and incompatibilism.

Compatibilism redefine free will to fit with determinism, and that is also not bothered much with a bit of indeterminism.

Incompatibilism just infers that if the assumption were true, we don't have free will (no matter if the world is deterministic or also has indeterminism).

However the monist physical reductionist assumptions, while popular, are not the only possible assumptions, so other writers suggest non-reductionism or dualism to rescue libertarian free will, with reference to concepts that science has not observed yet.

  • 1
    The reductionist perspective is absolutely wrong, it does defy science. Mental states have no physical properties at all, they are not physical, they cannot be reduced to or even described in terms of physics. Libertarian free will does not need to be "rescued", science has observed the ability to make decisions. Commented Oct 25, 2023 at 9:57
  • The question does seem to make it's premises and reasoning clear. Any "monist physical reductionist perspective" that it may be asked from is included in the premises. For alternative perspectives, you could probably be a bit more specific about which premises they would object to or where their reasoning would deviate (rather than merely pointing out that there are other perspectives).
    – NotThatGuy
    Commented Oct 25, 2023 at 11:33
  • I provide the OP with the philosophic terms to investigate the issue. Also I tried to keep the answer short.
    – tkruse
    Commented Oct 25, 2023 at 12:01

Deterministic vs random vs ???

I largely agree with you: neither determinism nor randomness allows for "free will" (even if some disagree about that).

But a libertarian free will proponent might say there is a 3rd thing, which either is free will, or allows for free will.

The issue there, however, is that we have no reason to believe such a 3rd thing exists (apart from our own desire to not be bound by the laws of nature, or our own belief that we have some existence above or outside of it), we have no idea how that would interact with observable reality, and we can't even conceive of a mechanism for such a thing.

Never mind all the evidence we have of consciousness being bound by natural forces: we know a lot about how the brain works on a physical level, and which parts of the brain do what, injuries to specific parts of the brain changes personality in predictable ways, brain-related disease has predictable effects on personality, many human behaviours are predictable (many with essentially 100% accuracy, especially on an individual level). That doesn't necessarily mean there isn't another driving factor behind consciousness, it would just be rather unnecessary and contrived to try to fit that into what we've already demonstrated. As our understanding of the brain has increased, the proposed non-physical part of our mind has shrunk correspondingly, or for some it's shifted to merely being "on top of" our brain (which seems to make it entirely unnecessary in terms of explaining anything).

free will requires us to be able to choose between different possible courses of action

Under this definition, one might argue that determinism allows for free will. To "choose" means to pick one of multiple options based on some criteria. There's no reason this cannot be done deterministically.

It's only when your definition of "choose" already presumes free will that determinism would not be possible. But then the above sentence would essentially reduce to a tautology: "free will requires free will".

Free will is commonly defined by "the ability to have done otherwise", i.e. if time were rewound (and you also reverted back to that earlier state), is there a possibility that you'd have chosen differently? But this seems to just be defining it as non-deterministic.

Under this definition, randomness could be considered free will, but it seems to only meet the "free" part, and not the "will" part: random actions by definition lacks any relation to meaningful intent or whatever circumstances you find yourself in.

Although there has been debate about the definition and such.


The logical error you are making is that you see probabilism as the opposite of determinism when you should explore indeterminism.

  • Determinism does deny free will and probabilistic randomness.
  • Indeterminism does not deny free will or probabilistic randomness.

Probabilistic randomness is the inherent inaccuracy between a cause and its effect. Regardless of the cause, the effects are never determined with absolute accuracy.

Free will, a.k.a. agency, is the ability to self-cause one's own actions, to insert new causes to the causal flow of events. This is not denied by any law of physics. The laws of physics only determine what is the effect for a given cause.

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    Can you provide any sources which demonstrate that humans have the ability to "insert new causes to the causal flow of events"? From what I've read, this is a highly controversial claim. Commented Oct 25, 2023 at 10:51
  • I don't know what you have read, but I cannot see any controversy about this obviosity. Spinal reflexes are caused by the stimulus. Voluntary actions are caused by the decision to act. Decisions are not caused as they are not physical events. Commented Oct 25, 2023 at 12:20
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    See IEP. Interactionism: mental and physical cause each other. Parallelism: mental and physical do not interact. Epiphenomenalism: Physical causes mental but mental causes nothing. Reductionism: Mental events are physical events. In short, 3 out of 4 of these are opposed to your belief, so perhaps it's not as obvious as you think. Commented Oct 25, 2023 at 12:31
  • All of them are against science, logic and common sense. I have no beliefs. Mental cannot be caused. Mental and physical do interact. Mental does cause physical actions. Mental events are not physical events. Commented Oct 25, 2023 at 12:42

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