Let's imagine that we live in a world with infinite universes. One of these universes is the same as the one we live in, except for one change: this morning I choose to cut off my leg for some reason, instead of drinking coffee.

As there are infinite universes, this universe must exist. Keep in mind that I had no reason to cut my leg off, so does this mean that free will contradicts the theory of inifinite universes? So we can only have one universe?

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    I don't know whether freewill could contradict the theory of infinite universes; although I personally believe the theory is false in any case (for other reasons). Yet the very fact that people can choose to act in such an irrational fashion certainly seems evidence of freewill.
    – Bread
    Oct 28 '18 at 16:21
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    First, infinity of universes does not mean that every possible one is realized, second, what your argument implies is that it is determinism, not free will, that contradicts realizability of all possibilities. Because the universe where you cut your leg without a cause can not be deterministic.
    – Conifold
    Oct 28 '18 at 21:30
  • In the first paragraph you say you chose to cut off your leg for "some reason". In the second, you say you had "no reason". Did you have a reason or not in this account?
    – alanf
    Oct 30 '18 at 8:01
  • I dont know i am not the one who choose to cut the leg off so i have no idea why i i did only assumed it wasn't free will because i would never see myself cutting off my leg
    – someone
    Oct 30 '18 at 11:53
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    The question does not even make sense. There is no contradiction between the idea of having the ability to make free decisions and the possibility of infinite universes where each of us would make different decisions. And since we have never seen another universe than ours to test this theory, it is not even wrong, just nonsense.
    – armand
    May 25 '19 at 11:37

I will attempt to make your argument more concise:

P1: Free will exists.

P2: The theory of infinite universes is true.

C1: (From P2) Therefore, there exist an infinite number of unique universes.

C2: (From C1) Therefore, in at least one of those universes I must freely commit a specific self-deprecating irrational action (e.g. cutting my leg off).

C3: (From P1 & C2) If free will exists, no agent can freely choose to commit an irrational self-deprecating action. (I can only assume this is what you assumed to invoke a contradiction). Therefore, either free will or the infinite universe theory is false.

C: The infinite universe theory is false.

What is required for the argument to work? Assuming the premises are true. Supposing the infinite universe theory entails every possible event happening.

Taking those as true, P1, P2, C1 and C2 are true.

But, the leap required from these to C3 is just inexplicable to me. Furthermore, it seems to me when you arrive at the desired contradiction, you randomly choose which premise is false (or maybe you have already concluded it is true).

So, I'd say even though I thoroughly disbelieve the infinite universe theory, it cannot be disproven by the existence of free will.

An aside note:

I was about to comment on the "large infinity" and similar concepts (found in other answers) by declaring them irrational, instead, here's the example which helped me grasp it.

Premise 1: An infinite number of flavours exist.

Premise 2: An infinite number of ice creams exist.

Conclusion: There exists at least one ice cream of each flavour.

The conclusion obviously cannot be determined from the premises. Since there could be an infinite number of ice creams of the same flavour.

So, an infinite number of worlds/universes doesn't guarantee all possible features.

Note: if the requirement is that all worlds (ice creams) are unique that seems to me to guarantee all possible features but I am not sure.

Cheers, Dominik

P.S. _I'm new here, don't know if it's acceptable or productive to revive old posts like this. Would appreciate feedback. Thx.

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    It is acceptable and productive to provide answers to old posts. I scan them myself using the search options and tags to find interesting questions. See stackoverflow.com/help/searching for how to search.There are even badges associated with editing and answering old questions such as revival and necromancer: philosophy.stackexchange.com/help/badges Jun 24 '19 at 13:22
  • Thanks a lot :D Is there a way to save comments or my own answers for later, like this one of yours? It's also interesting to find a fellow data scientist on the philosophy forum. (I'm not quite a DS but I'm currently working in the field)
    – Glorius
    Jun 24 '19 at 14:36
  • I don't know how to save comments outside of copying and pasting them in a file which I do with my own posts. The links I offered in my comment are bookmarks on my browser because I refer to them occasionally. I do "favorite" questions that I want to refer to later by clicking the star below the voting buttons. And there is also a philosophy meta site that might be useful: philosophy.meta.stackexchange.com/questions Many of us are not professional philosophers. We just find this a useful way to learn philosophy. However, some professional philosophers stop by. Jun 24 '19 at 14:58
  • Err... your note is completely wrong, but thankfully you said you are not sure. There are infinitely many even integers, but not every integer is even.
    – user21820
    Oct 11 '20 at 4:36

No, there can be infinitely many universes without there being a universe that contains each possibility or a world for every possibility. For example, an infinite number of possible worlds differ only with respect to one irrational number generated at a particular moment by an isolated random number generator.

To cover every possibility, you’d need an especially large infinity of worlds.

  • Oh I see what you are saying and that change could be totally not related to any human or creature with free will right ?
    – someone
    Oct 27 '18 at 18:57
  • How do real-valued random number generators work? Also: An "especially large infinity?" Do you have one in mind? How large would an infinite set be in order to guarantee that every event happens? And how do you measure largeness of infinities? Standard mathematical cardinals or perhaps ordinals? Or some other way? These two phrases of yours piqued my curiosity.
    – user4894
    Oct 28 '18 at 0:18
  • @user4894 any way you like, since possible worlds, as usually discussed, include those logically but not physically possible. Oct 28 '18 at 0:21
  • @ChristopherE Sorry, I added a second question as an edit and now I can't figure out which of my questions your response addressed. You conceptualized a real-valued random number generator and I'm curious as to if and how such a thing can exist consistent with contemporary physics even granting an actual infinity of multiverses. I'd strenuously argue the contrary, though not here since this site's not for that. Secondly (separate question) I am curious what the phrase "larger infinity" means to you. I know what it means to me, having studied cardinals and ordinals.
    – user4894
    Oct 28 '18 at 0:23
  • @user4894 and on the sizes of infinity, I had in mind a higher cardinality, but beyond that I’m sorry, I don’t know. I was wondering about that myself. It seems like the questioner could generate a problem by asking about something like the set of all physically possible worlds descended from this one, and there could be a way to argue that there are interesting implications of that. I was just giving the easy answer — infinite worlds per as don’t seem to me to be a problem. My previous reply was about how real number generators might work. Dodging! Oct 28 '18 at 0:27

As ChristopherE pointed out in his answer, there can be infinitely many universes without every possible thing occuring in some of them.

But I think that even if every possible thing occurs in at least some universe, we might still have free will. For example, if I'm presented with a choice right now, to do A, B, or C, there will be worlds ("universes", in your terminology) where I choose A, worlds where choose B, and worlds where I choose C. But why couldn't these be worlds where I freely chose A, B, or C? In fact, that's one of the criteria of libertarian free will (that the world is not deterministic). That in order for me to have freely chosen to do A, it must have been possible that I had chosen not-A instead.

  • Thats not what i said yes u can choose a or b or c but what i said was uf there is infinite universes where every possible thing would happen then there should be a universe where i choose to do something stupid and illogical which would mean that free will is imposaible if there are infinitely infinite universes where every possible thing happened
    – someone
    Oct 28 '18 at 16:25
  • I'm not sure I quite understand. For.s simplicity I limited it to 3 choices, A,B,C. But in practice I suppose there might be many more, maybe infinitely many. And your choice to do something completely irrational would be among the possible options A,B,C,... Even if there's infinitely many, as long as it's among the possible choices, you still could have chosen it, right? Oct 28 '18 at 17:15
  • I guess what I mean is, why does the possibility of completely illogical choices mean there's no choice? Oct 28 '18 at 17:16
  • The problem is that what is even free will and how do you choose to do something its not random cause if it was then society wouldn't exist so it must be A result of all of the previous experiences and memories a person has but then if its that how come i choose to do something completely diffeeent in another world? I am sorry if i am still unclear.
    – someone
    Oct 28 '18 at 17:27

"As there are infinite universes, this universe must exist.

That's a wild assumption to make.

Keep in mind that I had no reason to cut my leg off,

That's a wild assumption to make.

so does this mean that free will contradicts the theory of inifinite universes? So we can only have one universe?"

If we hold your assumptions to be true, you should rather conclude the inverse: you can have infinitly many universes while maintaining free will, because if you could assert that a minute change in the event-sequence of a univers does not cause an infinit ontological cost in the past, then you should be more inclined to do silly things. It's much like writing a novel, since you don't get to pay the bills, you can imagine living in a palace where you could drink out of a hot-chocolate fountain; in "real" life, you'd be more inclined to operate inside the constraint web that makes a sequence-event more likely than others - the "main" or "sole" event-sequence of that univers.

Good day


I believe that if the universe is infinite, it necessarily means that anything that can possibly be happening is currently happening.

However, I also believe in an infinite universe that things that are literally impossible cannot be happening anywhere in the universe, even if it's infinite. If the universe is infinite, an infinite amount of earths with an infinite amount of people will be simultaneously experiencing the universe, just like how you're experiencing the universe right now.

We are part of this infinite collection of people consciously experiencing the infinite universe together. Free will would not invalidate this concept. Us expressing our free will is simply the signature of what our Earth did in an infinite universe of Earths. This is assuming the universe is infinite.

I believe free will can coexist with an infinite universe. I personally believe the universe is way larger than the observable universe but may not be infinite.


To reply with a question: You say that "this morning I choose to cut off my leg for some reason, instead of drinking coffee," but actually you don't, do you? A hyper-clone, or counterpart, or whatever, does, but you yourself don't, unless you suppose that you are your hyper-clone or counterpart (or whatever). To rule out free will, wouldn't your model require the action you perform in your own world to automatically trigger the alternatives in the counterpart worlds? And then, vice versa, you would have it that the alternatives logically trigger your own action in your own world, wherefore voila, no free will.


Considerable uncertainty remains over how Many Worlds might work in practice. One suggestion is there might be a limit on the total information in an area of space linked to Planck-level data. Penrose suggests whenever the total uncertainty gets above an energy related to the uncertainty principle, 'collapse' happens.

Not relevant to this question though. For you to have cut your leg off or done something radically different, you would have had to BE different, YOU are your causal propensities. We face randomness though, both from non-linear dynamics, and of quantum kinds. YOU can face different events, and change, and become an altered person. The continuity is a useful fiction. But the same YOU can't make two different choices, the actual choices will be causally necessary.

Consider a coin flip, and you decide you will let it decide your actions, like Two Face in Batman, or similar to The Dice Man. Have you given up free will? Certainly not by standards that would apply in court. More generally, our free-ness of will relates to our ability to picture different futures, and to act intelligently in the present. So this choice to not have a choice is a way of relating to randomness, like we use all the time. Investing money. Speeding. The freeness of our will relates to our ability to imagine possible futures and the risks hazards & benefits of our actions relating to them - and that act of imagination has a definite informed relatiin to the future, based on past experience, but occurs now. The belief in alternative futures caused by our different actions, is a useful fiction that helps us choose how to behave.

The Many Worlds interpretation serves a different function, specifically related to quantum processes, and their indeterminacy. Niether a fundamentally random nor fundamentally pre-determined future impact free will. That is in an emergent explanatory layer, like the narrative grouping 'cells' or 'minds' which are complicated sets of atoms that have abilities to conserve that ordering. In Many Worlds, ordering principles like entropy increase & conservation of information, help us organise & navigate the probability space - some simple events like all the air in the room gathering in one corner are so unlikely they won't have happened even once in the age of the universe, so can be neglected - it would be like an 'infinite monkey cage' to write Shakespeare, we never truly have infinite time or material, the heuristic we use is it violates information conservation, which we use to distinguish between signal & noise.

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