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Determinism query

  1. Oct 13, 2014 #1
    My personal belief if you will is that we have free will. Anyway my question relates to the so called deterministic behaviour of a coin toss as opposed to a quantum decay.

    I think that we all agree that quantum physics displays truly indeterminate random behaviour. However I have heard it stated many times that even though there is quantum randomness at the micro level, at the macro level objects display normal newtonian determinism.

    My question relates to an example that is often given of say a coin toss. Apparently a coin toss displays determinism in principle because if we knew everything about the coin and we knew everything about every single air molecule and so forth that we would in principle be able to predict the coin toss which is fundamentally not possible with nuclear decay.

    However, this bugs me a lot because I do not see how even in principle the coin toss could be determined due to the fact that even though there may be multi trillions of air molecules involved, we are still in principle not able to know the position and momentum of any of them. So how can the coin toss be used as an in principle argument for macroscopic determinism.

    And this follows that the behaviour of the human being cannot be determined and therefore we do have free will due to the same reasons that the coin toss cannot be determined in principle.
  2. jcsd
  3. Oct 13, 2014 #2


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    Science Advisor

    You are right that the determinism in macro level objects is only approximate. It is impossible, even in principle, to know the position and momentum about every air atom and every coin atom exactly.

    As to the relevance of that observation to "free will". I see no possible scientific test to address the matter. So it's more philosophy than science and not proper subject matter for discussion here.
  4. Oct 13, 2014 #3


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    Staff: Mentor

    Jbriggs has it right.
    I'm closing this thread, although a more focused discussion about how classical deterministic behaviors emerge from the underlying probabilistic theory of quantum mechanics would be a reasonable topic (There are already some discussions along these lines in the QM subforum, where I'm moving this thread).

    If you want to explore the relationship between QM and free will (but not here! please!) you could give Roger Penrose's "The Emperor's New Mind" a try.... just be aware that a fair summary of the reviews would be "interesting, but profoundly unconvincing".
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