bluefugue

Can someone explain just *how* chaos theory says that physical laws are not *even in principle* predictable? I didn't get that impression from reading James Gleick's book on Chaos, but that was several years ago. My impression of chaos theory (****which I freely and completely and without any presumption admit is surely incomplete, as I am not, nor ever have been, nor should be in any way construed as, a scientist or an expert or even an informed layman in these matters****) is that it has more to do with the emergence of patterns in seemingly unpredictable, complex systems.

The point I am focusing on is "in principle." It is laughably obvious that the universe is not *in practice* predictable, and I am under the impression that quantum mechanics says the universe is not *in principle* predictable either. But how does chaos theory establish this?

madmax2976

bd-from-kg: Almost everything you say here is (IMHO) wrong.

Good. That’s what I’m looking for; reasons why the conclusion of the argument would be wrong.

According to the standard interpretation of quantum mechanics, the universe operates according to physical laws which involve an element of intrinsic randomness. If this is correct, the universe is not deterministic.

Lets assume the standard interpretation of quantum mechanics is correct and the universe is not entirely deterministic, but has “intrinsic randomness”. How would an element of randomness enable people to make choices? If things we’re random, then events would just happen for no reason – which is what randomness implies. Therefore, thoughts would just pop into our heads randomly. Could we really say we make choices if our thoughts are random?


quote:

2. This makes events/reactions within the universe predictable.

Not so. According to chaos theory, even if the universe is deterministic future events are not predictable, even in principle. More precisely, for any given degree of precision to which you choose to do your calculations, round off error (or errors in the values of the original parameter that you feed into the calculations) will cause the results to be significantly in error – to the extent that you will, for example, predict a major war that does not occur or vice-versa. And this point will come surprisingly soon. For example, if you do your calculations to 10,000 decimal digits, your results will be seriously in error (war vs. no war) in a few years at most.

First of all we do make predictions about events. The whole point of formulating laws is precisely because we observe repeatable behaviour in the universe. Reapeatability and prediction of phenomena is one of the core foundations of scientific investigation. If you let go of a rock – it will fall due to the laws of gravity.

Indeed, without this deterministic behaviour, I don’t see how it would be intelligible to say humans make choices. If events were not predictable, then my choosing to shoot someone in the head might or might not cause severe injury or death – it would become completely arbitrary for me to decide one action over another. It seems we require determinism in order to make meaningful choices at all. But the paradox seems to be that if events in the universe are determined, then our very actions might also be determined.

As I have also said, humans may not be able to make the predictions themselves due to the vast array of factors involved and our inability to measure precisely enough. (Choas Theory) But regardless, its appears that events are either deterministic or random, ontologically speaking. The ability of humans to choose in either situation seems to be a mystery.


quote:

3. The human brain operates according to physical laws making its events/reactions predictable, in principle. The end result of this of course would be that humans really don't make choices. We are constrained to do what we do because of universal laws.

Even ignoring the earlier errors, this conclusion is false. If I eat a candy bar because I want to eat a candy bar, it is an abuse of language to say that I am “constrained” to do it. I would be “constrained” to do it only if I were forced to do it against my will.

Well that’s the whole point. Do you have a “will”? Or do the events concerning you happen according to universal laws, and thus your “will” is only an illusion. On the other hand, if things are random, your ability to make choices appears just as illusory. There would be no cause for you to be the way you are or do the things you do. You’d just do them.

Note that the actions of Smith and Jones were caused, but the causes lay within themselves, and consequently they can be meaningfully said to have made a choice.

But what does this mean – “the causes lay within themselves”? Was there nothing that caused them to be the way they are or is the way they are a random happening? If events are random, keeping the wallet or giving it back would be a random event – there would be no “choice” involved.

But Phillips’ action was not caused by anything within himself (or if it was, the cause was simply that certain atoms happened to be arranged in a certain way at that particular moment), and therefore his action cannot be meaningfully called a choice. These examples should make it clear that that meaningful choice depends on the choice being “caused” by one’s own character and personality as they bear on the situation at hand.

Are our characters and personalities the way they are because they are determined to be that way or because they just randomly happened to be that way?

To the extent that an act is uncaused, or caused by transient factors that just happened to cause the decision to go one way or another (but might have caused it to go the other way if it had come a second earlier or later) it is not a meaningful choice at all. Thus determinism would not be incompatible in the least with the ability to make meaningful choices.

I don’t’ really understand you here. Either there is a causal chain of events that causes us to be the way we are and make the choices we do or there is not. If there is – it would seem our actions are determined. If there is not – our actions would seem to be random.

Mageth

bd-from-kg:

I have a problem with your wallet example. This holds true for any of the three men, but let's just look at the third.

He will never encounter exactly the same situation again. I mean "exactly" down to the quantum level. It is impossible to rewind time and let him repeat the test several times to get a distribution of his "random" response to finding the wallet. But if it could be done, might he have chosen differently given exactly the same circumstances? Our understanding of the universe and reason say he would make exactly the same choice every time the test is repeated. Thus it can be reasonably stated that he did not truly have "free will" in the matter.

I personally believe along this line. It is probable that in this natural universe we do not truly have "free will" Our genetics and our environment affect and direct every choice we make. Our consciousness (an emergent, but "natural", phenomenon - nothing supernatural there) models what we experience to make it seem we have a "free will" to choose, but in reality only natural forces affect our choices, and free will is an illusion. To claim a "free will" is to add something supernatural to the equation - a pixie in our heads that can magically alter the natural universe and subvert its laws.

However, because of the problems stated above, I don't think it's possible to predict the future of brain activity. [edited to add: but I may be wrong!]

Another theory along this line is the many worlds theory of David Deutsch. In such a universe, every possible alternative choice is made, and each fork splits into its own universe. So we just happen to be in the universe where man #3 kept the wallet. In another universe some happy fellow got his wallet back.

[ November 30, 2001: Message edited by: Magethlaro ]</p>

symtacs

interesting debate..

we believe that the universe is made of some fundamental laws which is essentially 'the theory of everything'. agreed.

now suppose, we know those fundamental laws and we make a big computer in which we feed those laws together with the current state of the universe.

technically, starting from the big bang, the computer should be able to predict everything just the way it is. it should also predict if i choose to take italian dressing or 1000 islands for my salad. we think its purely human decision purely random. to the surface it does appear random to us. but the decision is driven by connections of neurons which are made up of cells made up of atoms made up of subatomics, based on laws which we discovered and run through our computer. [the issue of its complexity doesnt matter].

current science leads us to this level. u may say scienfce is about physics and society doesnt matter but society is made up same atoms which are used in chem labs..

problem: if the computer computes the same output all the time, do we have free will? then i could hit a car and tell the judge that hey man if u put it in big computer it will produce the same result again.

so our freewill is deteremined. big deal. if i chose to eat island1000 instead of italian our computer should be able to compute that too.

but the problem comes if i tell the person, the result of computation, before he executes his choice. the person sits waiting for computer's response to what he will eat. wot if the person eats the opposite of whatever the computer shows as the answer? then our all knowing computer just couldnt predict the answer accurately.

this means that either such a computer is not possible, or its not possible to predict human behaviour from fundamental laws which are governing the brain, or there are no fundamental laws to begin with. i have a feeling there are no such laws. even if there are, they are infinite.

NialScorva

Determinism doesn't necessarily imply predictibility. We can't even calculate 3 body equations. We understand Newtonian and Quantum fairly well, and we can predict what will happen when you have to bodies in the system, but we can't solve the equations that describe three planets, or electrons. We can *approximate* to a high order of precision in many cases, but we can't actually solve them.

DanishDynamite

Symtacs:
It isn't possible, even in principle, to feed a computer with the current state of the universe. The only gadget large enough to encode this state, down to and below the states of vacuum flux, is the Universe itself.

Mageth

[edited to add: welcome syntacs]

but the problem comes if i tell the person, the result of computation, before he executes his choice. the person sits waiting for computer's response to what he will eat. wot if the person eats the opposite of whatever the computer shows as the answer? then our all knowing computer just couldnt predict the answer accurately.

The problem with your scenario is that you are changing the condidtions in the real universe by telling the person what his choice will be. There is therefore input in the real universe that is not in the computer. So the computer simulation and the real universe no longer match.

[ November 30, 2001: Message edited by: Magethlaro ]</p>

Mageth

Welcome, DanishDynamite.

It isn't possible, even in principle, to feed a computer with the current state of the universe. The only gadget large enough to encode this state, down to and below the states of vacuum flux, is the Universe itself.

Not possible, perhaps, in principle, but this is a thought expriment, and it's acceptable to postulate such a computer in a thought experiment.

Actually, you might in principle be able to perform the same experiment on a limited scale; start from a point in the near past and run a simulation of a portion of the universe "local" to the person in the test for a timeslice using prerecorded conditions of the "local" portion of the universe for the timeslice. But the problem I noted above with symtacs' example still holds.

[ November 30, 2001: Message edited by: Magethlaro ]</p>

madmax2976

I incorrectly stated my question in my initial post. My fault.

My question is not directly concerned with human ability to predict humans events. This does seem impossible based on the data and quality of data that would be required - I agree.

However, my question does concern the actual ontological status of our ability to make choices in a deterministic or a random universe.

Perhaps this states it better:

1. The universe operates according to physical laws, which means events will occur in accordance with those laws.

2. The brain also operates in accord with physical laws.

3. Therefore, human events/actions are actually caused by universal laws and therefore any sense that we make choices is an illusion.

The alternative seems to be the introduction of randomness into the mix, however I fail to see how randomness solves the mystery. If our thoughts are random, there would be no choice involved. We would just do what we do without reason.

Mageth

I agree with you. To say otherwise is to say that there is something outside of the physical/universal laws that allows us to affect the natural universe through our choices. In other words, it adds a supernatural element.