Laplacean Demon unable to predict any future state?

[trip]

If a Laplacean Demon existed, with full physical knowledge of the universe at a specific state, would it actually be able to predict the subsequent state of the universe at a later time given quantum indeterminacy? After all, given that a truly random factor is in play here, how could the demon predict a future state even a few seconds into the future? Remember that the demon's knowledge, though perfect, is restricted solely to a single moment.

Before you post:

1. I understand that at larger scales these random events might be 'absorbed' and the universe, as far as cause and effect concern us, would still be essentially deterministic.

Since the demon is keeping track of everything though, down to the smallest scales possible, any error it made would refute its supposedly flawlessly accurate predictive powers.

2. I understand that even if random events happened at this level, this would not create 'freewill' since it would just be another type of cause beyond our control, essentially no different than a predetermined cause as far as it affects us.

I'm simply asking, would the demon be able to do what the thought experiment assumes it can do?

[Kingreaper]

If a Laplacean Demon existed, with full physical knowledge of the universe at a specific state, would it actually be able to predict the subsequent state of the universe at a later time given quantum indeterminacy? After all, given that a truly random factor is in play here, how could the demon predict a future state even a few seconds into the future? Remember that the demon's knowledge, though perfect, is restricted solely to a single moment.

It depends which interpretation of quantum mechanics you subscribe to:

The two that come to mind are:

Hidden variables: If it's aware of the hidden variables it can predict perfectly,

Dimensional splitting: It can predict every dimension that shall arise

True randomness: It can't predict it. I find this interpretation rather disturbing, and puzzling personally, and refuse to accept it for the same reason I refuse any other final answer


A more interesting question to me is: Is i's prediction just a prediction, or is it's prediction also a world itself.

[t.w.]

Quantum randomness is relevant only at the sub-atomic level; and the predictions the Laplacean Demon is alleged to be able to make are at the atomic level and higher. He doesn't have to predict the positions of electrons
The statement 'predict the state of the universe at a future state' assumes the state of the universe at the atomic level and above will be predicted, because the random movements of sub-atomic particles have no effect exterior to the atom.

[TautologicalAxiom]

Good question...it's one I've also wondered about.

Quantum randomness is relevant only at the sub-atomic level; and the predictions the Laplacean Demon is alleged to be able to make are at the atomic level and higher. He doesn't have to predict the positions of electrons
The statement 'predict the state of the universe at a future state' assumes the state of the universe at the atomic level and above will be predicted, because the random movements of sub-atomic particles have no effect exterior to the atom. But how is this to be understood along side the multiple-worlds interpretation? Each possible event takes place in some universe or another, so doesn't this mean that random quantum effects do end up having a critical impact on outcomes on the greater- than- sub-atomic scale?

With the multiple-worlds theory, an alternate universe in which the fundies suceeded in taking over and establishing a theocratic America would depend on a huge bunch of electrons that went a certain way rather than the other, isn't that right?

Dimensional splitting: It can predict every dimension that shall arise I'm considering two ways that this could be said to work; either all that is involved is stating that all possibilities in accordance with the laws of physics will eventuate, in which case you don't need to be a Laplacean Demon to make this "prediction", or perfect knowledge about every kind of alternate universe that is sure to form would require knowing the exact state of every electron, which is impossible.

I never knew enough about this subject to have much confidence in what I said above, so the answers should be quite elucidating.

[Cacofonix]

Well, there you go

Kingreaper: "True randomness: It can't predict it. I find this interpretation rather disturbing, and puzzling personally, and refuse to accept it for the same reason I refuse any other final answer"

Anton Zeilinger (Google him), a cutting edge quantum experimenter mathemetician and philosopher, does believe that there will be one bit of information derivable from one yes/no question asked by the experimeter. His experience and hunch is that this is truly random.

I can't see why this is puzzling, disturbing or 'final'.

[untermensche]

If a Laplacean Demon existed, with full physical knowledge of the universe at a specific state, would it actually be able to predict the subsequent state of the universe at a later time given quantum indeterminacy? After all, given that a truly random factor is in play here, how could the demon predict a future state even a few seconds into the future? Remember that the demon's knowledge, though perfect, is restricted solely to a single moment.

Before you post:

1. I understand that at larger scales these random events might be 'absorbed' and the universe, as far as cause and effect concern us, would still be essentially deterministic.

Since the demon is keeping track of everything though, down to the smallest scales possible, any error it made would refute its supposedly flawlessly accurate predictive powers.

2. I understand that even if random events happened at this level, this would not create 'freewill' since it would just be another type of cause beyond our control, essentially no different than a predetermined cause as far as it affects us.

I'm simply asking, would the demon be able to do what the thought experiment assumes it can do?
Not with present day imperfect knowledge of how the universe works. But with perfect knowledge of position, and perfect knowlede of all properties of entities in the universe, and perfect knowledge as to how the universe worked, you might be able to do it.

[Hoodoo Ulove]

If a Laplacean Demon existed, with full physical knowledge of the universe at a specific state, would it actually be able to predict the subsequent state of the universe at a later time given quantum indeterminacy?Not with present day imperfect knowledge of how the universe works. But with perfect knowledge of position, and perfect knowlede of all properties of entities in the universe, and perfect knowledge as to how the universe worked, you might be able to do it.As long as the Demon doesn't tell me his prediction. Then things won't come out the way he tells. (Unless he predicts he's going to kill me right now.)

[trip]

As long as the Demon doesn't tell me his prediction. Then things won't come out the way he tells. (Unless he predicts he's going to kill me right now.)

That's a really interesting point. If there is no freewill because of determinism, then the demon should be able to tell you exactly what you'll do in the next minute. But if he told you this you could just do something else, right? But he would have taken that into account and predicted what you'll do given the knowledge of what he's told you, but then you could simply do something other than even this modified prediction, but he would have taken that into account...

So basically, even without quantam indeterminacy, the demon could only predict the future if and only if he kept the prediction a secret from you, and if he told you of it, the demon would be completely unable to predict what you'd do since you could always do otherwise.

[untermensche]

As long as the Demon doesn't tell me his prediction. Then things won't come out the way he tells. (Unless he predicts he's going to kill me right now.)
The Demon would know exactly what you would do, should he change prior conditions and inform you of his initial prediction.

You simply have two deterministic states. One where the Demon does not inform you, and another where he does.

[Hoodoo Ulove]

You simply have two deterministic states. One where the Demon does not inform you, and another where he does.I wasn't arguing for or against determinism, merely pointing out that he could not always correctly predict my behavior to me. A trivial point, perhaps, but true. It does maybe point out that despite some similarities, there are important differences between people and billiard balls.

[Kingreaper]

I can't see why this is puzzling, disturbing or 'final'.

If something is random, there is no reason why it is one state or the other.

If something is merely unpredictable, there may be a reason, you just don't know what it is yet.

Randomness is a final answer, it doesn't let you ask "why?". I don't like final answers.

[untermensche]

I wasn't arguing for or against determinism, merely pointing out that he could not always correctly predict my behavior to me. A trivial point, perhaps, but true. It does maybe point out that despite some similarities, there are important differences between people and billiard balls.
I'm saying he could always predict your behavior.

If he told you something, he would know exactly how you would react to that.

[Hoodoo Ulove]

I'm saying he could always predict your behavior.

If he told you something, he would know exactly how you would react to that.This demon, as I understand him, is merely omniscient, not omnipotent, right? If he tells me I will choose door number one, how am I prevented from choosing door number two? Knowing, as he would, that I am a contrary son of a bitch, he would indeed know I would choose the door other than he predicts, but he would be stymied nonetheless.

[untermensche]

This demon, as I understand him, is merely omniscient, not omnipotent, right? If he tells me I will choose door number one, how am I prevented from choosing door number two? Knowing, as he would, that I am a contrary son of a bitch, he would indeed know I would choose the door other than he predicts, but he would be stymied nonetheless.
No matter what the Demon tells you, since he knows how all stimulation will effect you, he knows exactly how those words will effect you.

You will think you have made some choice to fool the Demon, and he will know you are going to make it before you do.

[Hoodoo Ulove]

No matter what the Demon tells you, since he knows how all stimulation will effect you, he knows exactly how those words will effect you.

You will think you have made some choice to fool the Demon, and he will know you are going to make it before you do.No, I will not think I have fooled him. We are playing an asymmetric game, and he can't win. First player at tic tac toe need never lose, even if his opponent knows his strategy.

[Kingreaper]

No, I will not think I have fooled him. We are playing an asymmetric game, and he can't win. First player at tic tac toe need never lose, even if his opponent knows his strategy.

I assume you're talking about 3d tic-tac-toe, because the 2d version is symmetric, in that neither player need ever lose, but neither player can ever win, because in a reaonable game a draw is certain.

[untermensche]

No, I will not think I have fooled him. We are playing an asymmetric game, and he can't win. First player at tic tac toe need never lose, even if his opponent knows his strategy.
You are playing no game. He has full knowledge of what you will do before you do it. No matter what he tells you, he knows how that will effect you and how you will react to it.

You cannot bluff, or fake, or make any move that is not known before hand.

[Black Badger]

You are playing no game. He has full
knowledge of what you will do before you do it. No matter what he tells you, he knows how that will effect you and how you will react to it.

You cannot bluff, or fake, or make any move that is not known before hand.

But this isn't about whether the demon is fooled or not. The point is, he's incapable of giving a person an accurate prediction of their own actions, because they can choose to do the opposite of what he says they will.

Even if you allow him full predictive power in his own right, his inability to share his knowledge is interesting, no?

[goldingds]

It seems to me that to be a true Laplacean Demon, he should be able to share his knowlege. If he shares his knowlege, he will know the outcome.

A slightly related question: Can the Laplacean Demon deny himself? Does he know what he himself will always do?

edit: I have one more question. Can the Laplacean Demon tell the past? Sorry if that's dumb, I'm new to this whole "philosophy" thing.

[untermensche]

But this isn't about whether the demon is fooled or not. The point is, he's incapable of giving a person an accurate prediction of their own actions, because they can choose to do the opposite of what he says they will.

Even if you allow him full predictive power in his own right, his inability to share his knowledge is interesting, no?
By telling a person of the prediction the Demon has actually changed the conditions the prediction was based on. So the second the Demon tells a person about a past prediction, that prediction changes.

The predictions will change if conditions the predictions were made under change.

[dongiovanni1976x]

That's a really interesting point. If there is no freewill because of determinism, then the demon should be able to tell you exactly what you'll do in the next minute. But if he told you this you could just do something else, right? But he would have taken that into account and predicted what you'll do given the knowledge of what he's told you, but then you could simply do something other than even this modified prediction, but he would have taken that into account...

So basically, even without quantam indeterminacy, the demon could only predict the future if and only if he kept the prediction a secret from you, and if he told you of it, the demon would be completely unable to predict what you'd do since you could always do otherwise.

there is no "modified prediction". The demon is aware of all that has happened and all that will happen at the same time. As a result the demon doesnt change its mind by going, "I will tell trip x, y or z" which would then be a new variable that will cause your thoughts and concomitant actions to alter the future. It is best to call this demon a super computer that was imputed with the location, spin, velocity etc of every particle in this and every possible universe as well as every law of physics both known and unknown. From this information the demon computer can retrieve any moment in time in any and all locations both forward and backward.

[untermensche]

there is no "modified prediction". The demon is aware of all that has happened and all that will happen at the same time. As a result the demon doesnt change its mind by going, "I will tell trip x, y or z" which would then be a new variable that will cause your thoughts and concomitant actions to alter the future. It is best to call this demon a super computer that was imputed with the location, spin, velocity etc of every particle in this and every possible universe as well as every law of physics both known and unknown. From this information the demon computer can retrieve any moment in time in any and all locations both forward and backward.
If the Demon is as trapped in the same chain of cause and effect that it observes, then anything it thinks it knows may simply be what all the causes have made it believe, and not what is truth.

This Demon, if it is to really know anything, must be removed from the cause and effect it observes.

And therefore if it passes some prediction on to those trapped in the chain of cause and effect, the Demon has therefore changed the conditions the prediction was based on.

[t.w.]

But how is this to be understood along side the multiple-worlds interpretation? Each possible event takes place in some universe or another, so doesn't this mean that random quantum effects do end up having a critical impact on outcomes on the greater- than- sub-atomic scale?

No, they wouldn't.


With the multiple-worlds theory, an alternate universe in which the fundies suceeded in taking over and establishing a theocratic America would depend on a huge bunch of electrons that went a certain way rather than the other, isn't that right?

The random events which occur inside an atom have no bearing on what happens outside it. An exception is when a conscious entity uses that randomness to determine a real-world event, e.g. Schroedinger's Cat. So I suppose, if this happened, the Laplecean Demon would be in trouble. but it hasn't happened yet, and I don't know if it could happen.

[dongiovanni1976x]

If the Demon is as trapped in the same chain of cause and effect that it observes, then anything it thinks it knows may simply be what all the causes have made it believe, and not what is truth.

This Demon, if it is to really know anything, must be removed from the cause and effect it observes.

And therefore if it passes some prediction on to those trapped in the chain of cause and effect, the Demon has therefore changed the conditions the prediction was based on.
No disagreement here

[mirage]

No, they wouldn't.



The random events which occur inside an atom have no bearing on what happens outside it. An exception is when a conscious entity uses that randomness to determine a real-world event, e.g. Schroedinger's Cat. So I suppose, if this happened, the Laplecean Demon would be in trouble. but it hasn't happened yet, and I don't know if it could happen.

This is nonsense, I'm afraid.

Nucleus decay is stochastic and it can obviously have very large real world effects. In fact, in principle this "quantum randomness" is not limited to microscopic objects.

Physics as we understand it is a highly non linear system and any quantum noise is amplified, not cancelled out

Ignoring quantum weirdness for a while, if the demon is part of the physical system, it cannot predict the future states of the system perfectly because no system can represent it's own state completely.

[sweetiepie]

if the demon is part of the physical system
hopefully, no demons are part of the physical system

[t.w.]

Nucleus decay is stochastic and it can obviously have very large real world effects. In fact, in principle this "quantum randomness" is not limited to microscopic objects.

Suppose so - I thought 'stochastic' wasn't quite truly random; only unpredictable, as opposed to uncaused.

[Canard DuJour]

Nucleus decay is stochastic and it can obviously have very large real world effects. In fact, in principle this "quantum randomness" is not limited to microscopic objects.

Physics as we understand it is a highly non linear system and any quantum noise is amplified, not cancelled out

Ignoring quantum weirdness for a while, if the demon is part of the physical system, it cannot predict the future states of the system perfectly because no system can represent it's own state completely.Indeed and isn't it in the making of macroscopic observations (or measurements) that determinism fails? The question is what exactly constitutes an observation? Does a mouse make observations? An ant? A phototropic micro-organism?

If the demon makes the same kind of observations as we do, then they are subject to the same indeterminism. If not, then he observes a strange but deterministic world of wave-like interference between "linear superpositions" of divergent possibilities. But he still couldn't predict what we will observe.

Determinism might be preserved if there is some "hidden variable" determining wave collapse. But there is also the possibility - as some seriously suggest - that the variable is something to do with us. Which isn't really such a strange idea, but turns the question on its head.


(ETA : mirage, I know I'm not telling you anything, just using your post as a springboard for my 2 pence worth)

[Canard DuJour]

Suppose so - I thought 'stochastic' wasn't quite truly random; only unpredictable, as opposed to uncaused.
Right - causality is preserved but determinism fails and the demon is subject to the same limitations we are.