Let there be a person that acted in some way. Also there is another person who had predicted that behaviour of first person.

Does the first person has free will? Is it just possible to do something predictable and have free will at the same time?

First of all i define free will as skill of making decisions independently from external factors.

I know that there are different branches of thoughts about freedom of choice and determinism such as compatibilism but i would like to focus only on this case i introduced at the beginning.

I would like to know whether this may be answered just by logical calculus or it is a more complex problem.

In my opinion it follows like that

  1. We know for sure that given person is going to do specific action.
  2. There were a factors which made decision of that person.
  3. Then that person had no choice since it was predicted what would done.

Is my reasoning correct? Does it has a gaps? Or maybe my definition of free will is incorrect.

  • Do we know anything for sure and does that matter for making good predictions? I can see how a person could make a prediction of what I will do and be right. That might still only imply that the person knows me well enough to predict what I am most likely to freely choose to do. That is how I would answer this question, but I don't think that is what you are looking for. Commented Aug 8, 2019 at 14:16
  • I'd add that confirmation bias makes it seem as though we can for sure predict certain things, when in fact we can only make extremely educated guesses.
    – jhch
    Commented Aug 8, 2019 at 16:55
  • We may know for sure that a person will act so and so simply because the person already decided (freely) to do so, or because some aspects of behavior (like instinctive responses) are not free. But generally your kind of argument is discussed extensively in connection with divine providence, and is known as the argument for theological fatalism. It is not a matter of simple logic and ultimately turns on what is meant by "foreknowledge" and "free". There are ways to massage one or both to make them compatible.
    – Conifold
    Commented Aug 9, 2019 at 1:57

4 Answers 4


Free will is having a choice. Just because one can predict what choices another will make does not mean that the actor does not have choices.

Computers do not have free will. They do what they are programmed to and cannot choose to do otherwise.

People, on the other hand, almost always have choices. Sometimes the choices are dire ("Give me the combination to the safe or I will horrifically murder everyone you care about."), but, still, the person has a choice and has free will.

One can postulate situations where none of the available choices has any effect ("Lift this car, or someone will die"), but that is simply an impossible situation, not a lack of free will.

  • 3
    The term "free will" has different meanings for different people. There are at least four different meanings that “free will” is discussed frequently (for example, see this ref). The meaning in your answer is one of them. In this meaning, free will exists. But in some meanings, such as the one that requires that, to be free will, the will must not be predetermined by anything (e.g., natural laws, god/gods, or supernatural forces), free will may or may not exist, depending on whether determinism is false or true, respectively.
    – user287279
    Commented Aug 9, 2019 at 8:56
  • I think the question is moot unless we assume free will exists. As for whether determinism is false or true, that has been experimentally proven to be false, but that's another discussion. Commented Aug 9, 2019 at 14:45
  • 1
    I don't think everyone agrees with you that determinism has been experimentally proven to be false. This subject is still not settled yet and is widely being debated in many forums. And from Stanford Encylopedia of Philosophy Causal Determinism (revised Jan 21, 2016): there is no agreement over whether determinism is true (or even whether it can be known true or false).
    – user287279
    Commented Aug 9, 2019 at 15:58
  • Not everyone agrees that cigarettes cause cancer or that Global Warming is real, and yet... ;-) Commented Aug 9, 2019 at 16:36
  • 2
    "As for whether determinism is false or true, that has been experimentally proven to be false" ,,,has it? If you're referring QM, interpreting it as indeterministic requires just that... an interpretation where it is indeterministic. No experiment that I'm aware of has proven determinism false.
    – H Walters
    Commented Aug 10, 2019 at 11:45

Because you are speaking of prediction of a man's action you are in the position when that individual is an object for you. Objects cannot be free, they could be casual at max. Objects move within probabilities and laws (objects do not act, they move, their "acting" is the animation from your side). When thinking of an object and having knowledge of it, who is free is you, but you are not an object of the consideration.

Individuals as persons are free, but they are not objects. You cannot have "knowledge" about a free actor, who acts within his possibilities and freedom. At max, you could have expectations about him, not predictions (you can have some knowledge about his role, but not about the actor-in-role). In expectation (and generally vis a vis a free entity) you are positioned at the edge of becoming an object yourself in front of the free one who is not an object. This is the apprehension of an alien freedom.

In short, aspects of objectivity and of freedom are different "worlds", so asking if a free someone is predictable or not is a prohibited, illegal question. If someone other than me can be free the opportunity of their freedom must be taken from the beginning as an assumption, and then the question of predictability cannot be risen anymore. It is reasonable to argue whether one is free or not from the first person (emic) perspective, but it is silly to do from a third person (etic) perspective.


Although I am a determinist myself, there are some misconceptions about free will and predictability.

Quantum Physics (a set of the most successful theories out there) suggests that our Universe is not ABSOLUTELY, but only partially, predictable. If you have a particle P that is in a superposition of states (which means that it can have spin-up and spin-down at the same time), then we measure its spin: the superposition will be destroyed and the particle will take spin-up or spin-down (and not both). And there is nothing in modern physics that can predict what spin it will take, and physicists only talk about the probability of measuring spin-up or spin-down (like 80% spin-up and 20% spin-down)..etc.

So, fundamentally speaking, the Universe is unpredictable in essence. If we turn the clock back to 7 million years ago, nothing in the Universe guarantees that humans will evolve, there is evidence that goes against physical determinism, in this sense.

Philosophical determinism on the other hand (that we have no free will) is essentially different. Although nothing is totally predictable in the Universe, this does not necessarily mean that we have free will (since we do not have control over the quantum world, or whether particles measure spin-up or spin-down), as it turns out : we, too, submit to the unpredictability of the quantum world, regardless of our own free will.

Suppose that a murderer has no free will : the act of murder is a result of what happens in the brain, sets of neurons fire as a result of different stimuli, which is a direct result of what happens in the quantum world, where particles assume different unpredictable values for their different features (like spin, an electron in this neuron decided to take spin-up, another electron took spin-down ...etc), and all these quantum phenomena are physically non-deterministic (physical determinism is false), although the murderer himself does not have any control over it (philosophical determinism maybe true, remember : this is philosophy, so maybe ).

As you can see from the previous example, we can conclude 4 conditionals :

PREDICTABLE : You can absolutely and totally predict what will happen in the system, in principle. That is: Physical determinism is true.

FREE WILL : Philosophical determinism is false.


Those are true premises I guess, simply because if physical determinism is true then it is necessarily the case that we can never do something that is independent of the physical world : We did it because the physics says so.

So, if the whole Universe is predictable in principle, then no free will. This answers your question.

I add that, there are 2 false premises (in my opinion):


These two are equivalent premises, but they are false premises.

If you have no free will (like the murderer in the previous example), it does not necessarily mean that you are 100% predictable. Because your brain is also subject to quantum phenomena that are themselves unpredictable.

Note : As I am no compatibilist, I did not talk about that position.


Absolute predictability of a person's behaviour by other people is impossible (even if the person just died). There could be a very high degree of predictability; this would imply strong correlations between predicted and predicting - maybe they are identical twins with a very strong understanding of each other and in very good agreement, so both exercicing their free will while being predictable.

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