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Does the world operate deterministically?

  1. Apr 27, 2005 #1
    I am amazed by the number of times I keep having the same debate, in various threads, about the true nature of determinism. Many people seem to conclude that the principles and experimental results of quantum mechanics, and in particular Heisenberg's uncertainty principle, prove that the world operates indeterministically, at least at a quantum level.

    I wish to show this conclusion is incorrect.

    First we must distinguish between the meanings of Determinability and Determinism (it is important to understand that these words have different meanings).

    Definition of Determinism
    The universe, or any self-contained part thereof, is said to be evolving deterministically if it has only one possible state at time t1 which is consistent with its state at some previous time t0 and with all the laws of nature.

    Definition of Determinability
    The universe, or any self-contained part thereof, is said to be determinable if it has only one possible state at time t1 which can in principle be predicted (determined) by an agent (observer) based on a knowledge of its state at some previous time t0 and with all the laws of nature.

    Clearly, Determinism is an ontic property of a universe, and neither its definition nor existence is dependent on either observers or observation, ie a universe operates either deterministically or it does not, regardless of whether there are any observers around to know about it.

    Determinability, on the other hand, is clearly an epistemic property of a universe, it is dependent on the presence of an (in principle) observer, because it is defined in terms of the knowledge such an observer can have about the universe.

    The question posed in this thread is : Does the world operate according to the definition of determinism? (The question NOT posed here is "does the world operate according to the definition of determinability?")

    Epistemic Determinability vs Ontic Determinism
    The principles and experimental results of quantum mechanics, and in particular Heisenberg's uncertainty principle, show that there is an in-principle limit to our knowledge about the world - we have an "epistemic horizon" beyond which we are unable, in principle, to gain knowledge. This is characterised by Planck's consstant, and it places a lower limit on our ability to distinguish between determinism and indeterminism as true (ontic) properties of the world. In other words, we simply cannot know whether the quantum world is truly (ontically) deterministic or not.

    In absence of any conclusive experiment or evidence either way, it follows that if one believes the world is either deterministic or indeterministic then this is simply a matter of faith, and not one of science.

    The correct scientific answer to the question "Does the world operate deterministically?" is therefore "we simply do not know".

    Niels Bohr brainwashed a whole generation of physicists into believing that the problem had been solved
    Murray Gell-Mann


    We might ask the additional question : "Why do so many people seem to believe the world is not operating deterministically, when there is in fact no scientific basis for such a belief?"

    I believe there are several possible answers to this second question :

    1 Amongst many humans, there is a intuitive feeling of "free will" which naively seems at odds with the idea of a deterministic world. This naive intuition over-rules rational thinking and causes a mis-placed emotional belief in indeterminism. There is not much I can say to this except - please try to look at the issues open-mindedly and rationally, rather than intuitively and emotionally.

    2 Many humans confuse ontic determinism with epistemic determinability. I hope my clear definition and explanation above has cleared this up.

    3 Many humans are influenced by the propaganda that continues to be promulgated by learned scientists who, for one irrational reason or another, believe that the world is somehow indeterministic. To these people I say : Be more open-minded and critical, and question the basis for such beliefs. If you follow my above argument you will see such beliefs are founded more on faith than on rational scientific thinking.

    MF
    :smile:
     
  2. jcsd
  3. Apr 27, 2005 #2
    May be you are confusing determinism with (temporal) causality.
    You are free to use your own definitions and build logical conclusions based on these definitions. However it is dangerous to mix your own definitions (interpretations) with other ones that are not the same (except for the words) to make general conclusions/extrapolations.

    Seratend.
     
  4. Apr 27, 2005 #3
    IMHO it is dangerous to enter into any debate with clearly defining the concepts being debated.

    Would it be correct to interpret your comments above as meaning that you disagree with one or more of my definitions?

    If so, would you care to explain which of my definitions you disagree with, and why?

    MF

    :smile:
     
  5. Apr 27, 2005 #4
    MF is not currently loged on, but I can predict what he will ask. so I ask for him to save time (and because I want to know):

    What is your definition of causality?

    Until you explain the difference to me, I admit to some confusion. The only difference I see is that in a deterministic universe, causality certainly is always operating, but in a non deterministic universe, causality, as most people understand this work, may not always operate, especially if what I call genuine free will exists.

    I would BTW add a fourth possible reason to MF's list of reasons why most people tend to rule out the possibility of a deterministic universe, which is related to his first (the free will belief bias). MF probably knows it, but is too modest to have included it.

    (4) Most people either can't (or don't want to bother) to think as carefully (with well defined terms, etc.) as he does as simple assume that quantum uncertainty "proves" the universe is not deterministic.
     
  6. Apr 27, 2005 #5
    Well, that's precisely the problem. In physics and math we like to define precisely the concepts before, without them we can almost always say what we want. In QM theory the postulates are self coherent, only interpretations of QM words almost always lead to false conclusions/incoherencies.

    That's the problem: they are definitions: we can take them as true or false (it is a logical choice) and make logical conclusions based on these definitions. However, before that, we must prove that they are self consistent: this is the main difficulty. I.e. I do not know if your definitions are consistent or ill defined, it is you job to prove they are self consistent (i.e. you have to build demonstration).
    Now one of the common dangers with the definitions is their labelling (e.g. determinism). 2 different definitions with the same label does not mean they are identical (i.e. yours and the other ones).
    In your post, you are mixing different definitions using the same label to make certain (surely unlogical) conclusions. e.g. The correct scientific answer to the question "Does the world operate deterministically?" is therefore "we simply do not know".


    Seratend.
     
  7. Apr 27, 2005 #6
    There are many definitions of causality (one is to take an english dictionnary). I do not know all. The first one is the existence of a function, i.e. a=f(b), another one a partial ordering relation (like =>). In QM (and more precisely QFT) we have other possible definitions: the clustering principle (weinberg), etc ...
    The definition of MF is what I call a naive one (in a non pejorative sense). He assumes we describe the universe properties by a single time parameter. This is almost the newtonian/gallilean view (the absolute time). Now, we have dicovered, thanks to relativity and QM theories, that there are other forms of causality definitions.
    Therefore, the danger comes from the mixing of these different definitions to build unlogical conclusions.

    Please try to give your self coherent definition of "genuine free will" in a non "determinsitc" universe. (based on the fact that your deterministic definition is false). Otherwise, we may developp all the conclusions we want.

    That's again a conclusion without self coherent definitions (universe, deterministic defs in the context of QM theory).

    Seratend.
     
  8. Apr 27, 2005 #7

    ZapperZ

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    So how did this thread escaped from the Philosophy section? Was the warden asleep at the guard tower? :)

    Something like "... it is dangerous to enter into any debate with clearly defining the concepts being debated.... " can only belong there.

    Zz.
     
  9. Apr 27, 2005 #8
    I hope you are not suggesting that true science proceeds on the basis of undefined concepts? :biggrin:

    Clear definition of concepts forms the basis of all science (except of course for those of us who wish to obfuscate).

    MF
    :smile:
     
  10. Apr 27, 2005 #9
    Yes, However, currently, as there is not much activity on PF, we may try to focus this thread into "How it is difficult to build self coherent definitions before making physical conclusions" ; )

    Seratend.
     
  11. Apr 27, 2005 #10
    I am confused, I think there is a misundertanding of your sentence "it is dangerous to enter into any debate with clearly defining the concepts being debated". I interpret it as "defining clear concepts are dangerous to start a debate". This point of view is more related to phylosphie (definitively to politics ;) than sciences (or may be physics).

    Seratend.
     
    Last edited: Apr 27, 2005
  12. Apr 27, 2005 #11
    We agree then, that it is important to define concepts being debated.

    Can you explain what you mean by "QM word"?
    "Determinism" is a word in the English language, I am not aware that it is a "QM word"?

    Are you perhaps trying to say that "interpretations of QM almost always lead to false conclusions/incoherencies"?

    Agreed.

    I have not said that my definition is the only possible definition. I have asked whether you agree with it. You seem not to want to answer.

    What "different definitions using the same label" am I using? I do not believe this is a correct statement, can you elaborate please?

    In what sense is this a "mixing of different definitions using the same label"? I have defined very clearly what I mean by determinism.

    Perhaps you are suggesting that I have not defined "deterministically"? I agree. The correct question, given my definitions, should have been "Does the world operate according to determinism?".

    Determinism is clearly defined.

    MF
     
  13. Apr 27, 2005 #12

    ZapperZ

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    Re-read the quote I attributed to you.

    Zz.
     
  14. Apr 27, 2005 #13
    ooops, I must admit to a typo. My apologies.

    I meant to type "it is dangerous to enter into any debate without clearly defining the concepts being debated".

    Must learn to type more slowly and carefully.

    Thanks for pointing out my error.

    MF
    :smile:
     
  15. Apr 27, 2005 #14
    I AGREE, but I asked for your definition so I would know what you are taking about.
    I won't for two reasons, most important is that I can not give one that satisfied MF and other careful thinkers. I can tell many things it is not. (E.g. It is not based on the freedom of the uncertainty principle of QM - these probabilistic results do not provide me with any option for GFW that is better than tossing a coin does.)
    Second reason is that ZapperZ has a good point. this thread must say focused on the quantum mechanics aspects of this. Thus only as Free Will relates to QM is it appropriate to discuss FW (or GFW) here.
     
    Last edited: Apr 27, 2005
  16. Apr 27, 2005 #15
    yep, sorry, my mistake. I made a typo in my original post. :blushing:

    Thanks

    MF
    :smile:
     
  17. Apr 27, 2005 #16

    ZapperZ

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    Fine. Let's LEAVE it at that. No one can say the world is deterministic, and no one can say the world is indeterministic, FOR NOW. Now can we go on to something that actually is productive?

    Zz.
     
  18. Apr 27, 2005 #17

    DrChinese

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    You gotta love him.
     
  19. Apr 27, 2005 #18
    It seems to me also that it is appropriate here to focus on the need for clear definitions in QM. As i can not define a QM "observation" {other than by the nearly (if not completely) circular form: "Something that causes a mixed state wave function to collapse into a pure eigen state." }I would appreciate it if someone would try.

    The main unhappiness I have with the fantastically successful QM (Its predictions, even one that seem to be impossible to me, like quantum entanglement, have turned out to be confirmed by experiments.) is that it seems to me to logically incomplete: It requires something ad hoc, outside of the QM theory, namely an "observation" to interrupt the smooth and deterministic evolution of the wave function that one can, at least in principle, compute with the Schrodinger equation.
     
  20. Apr 27, 2005 #19

    DrChinese

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    OK, I am a sucker for these discussions anyway...

    1. So I will counter: Perhaps there was not conclusive evidence either way 75 years ago. But EPR+Bell is very persuasive if you were previously on the fence. If there are no hidden variables, then time does not have the property you ascribe to it in your definition. The state of the system at T1 is dependent not only upon T0 in the past, but also T2 which is in the future.

    2. In addition, there is plenty of evidence that the universe is not in a single state at T1 as you suppose. It is in a superposition. This can be seen in the double slit experiment, for one.

    So the point is that your conclusion fails because there is counter-evidence to your hypothesis. Now, you may reject that evidence. But doing so ignores its scientific acceptance; its acceptance is why books talk about an indeterministic universe.
     
  21. Apr 27, 2005 #20
    I type both slowly and inaccurately and thread is currently so active that by time I am done, MF and others may have responded, but I want to put in my one penny:

    On your (1) I think you are incorrect and MF is OK. If the universe is deterministic, then acts at T2 having influence at T1 is ok. Think of all history (including what you and I now call the future) as being a recorded movie - that we experience "now" by "now" or in the evolving time you say MF is misusing.

    On your (2) I don't think MF has ever denyed the possibility that QM is indeterminate. I.e. He would accept that the UP of QM limits our knowledge to be as if there are mixed states existing. Your "superposition of states" is no problem for him. He only wants to keep open the possibility that this is not fundamental, but only epistemic, if the universe is deterministic. I'll stop on (2) as he can better defend his view than I can. - my only real contribution, if any, is on (1) above.
     
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