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Heisenberg's Uncertainty Principle, Determinism and Free Will

  1. Oct 3, 2011 #1
    Heisenberg's uncertainty principle only seems to have implications for our understanding of the body of knowledge produced by science, not reality itself. The uncertainty comes from the inability to make two separate measurements, since each measurement will disturb the system and change the remaining attribute. This implies that objective reality is still deterministic, albeit unpredictable to us since we can't measure it accurately enough. In other words, the map (science, our measurements) is not the territory (reality). It is an approximation, a very accurate one at that, but still not identical to the real thing.

    In concrete terms, this means little, since while the system may be deterministic, it's random from our perspective. Nonetheless, it does have profound philosophical implications since if quantum mechanics (in the objective, not scientific sense) are deterministic, and so is every other level leading up the scales, then free will must be an illusion. In fact, I think that the concept of free will is the elephant in the room when in the presence of scientists. Even http://www.youtube.com/watch?v=aJP-1fNSd38" hints that the evidence points to no but doesn't want to say it outright.

    So what do you all think?

    I just noticed that there is a similar thread on this subject but I feel that this is addressing a different point.
    Last edited by a moderator: Apr 26, 2017
  2. jcsd
  3. Oct 3, 2011 #2


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    Whatever "reality itself" means - let's think of it just as a black box - the quest of science would still to try to gain knowledge of this black box in terms of how it responds to interactions. Our actions are reflected by our expectations (knowledge).

    So the limits of what we can infer from the black box, due to the nature of the inference process itself, is highly relevant.

    No offernse meant, but my personal thinking is that to ponder what is really in the black box, by trying to bypass the inference process where we query the box seems irrational, because it isn't verifiable and defendable in any remotely objective way - which is to me the definition of rational beleif of science, as oppose to religious beliefs.

  4. Oct 3, 2011 #3


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    Or maybe not so little. If free will is an illusion, then EPR correlations can, at least in principle, be used for the (illusion of) superluminal signalization:
  5. Oct 3, 2011 #4


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    If we by "free will" aren't talking about humans, but in the sense of a systems freedom of choosing action as placing bets that appears in the decision theoretic abstraction then at least I can related to the question and it becomes a little more interesting.

    In that sense, my opinon isn't that "free will" is an illusion, but rather that it's observer dependent, for the same reason subjective probabilities are.

    I read the abstract of Demystifiers paper and I certainly share the view that measurement theory must incorporate observers as well, but you can do that in two ways. Either by looking for an even more external view which incorporates the observer as well in terms of a mathematical god's view or realist view - or you consider that the measurethemy THEORY itself actually is encoded in the observing system and that the theory itself (including hamiltonians and state spaces) is evovling along with the interactions.

    In the latter view which I subscribe to it's also true that the "degree of free will" changes with perspective/observer.

    The point of debate is IMO more if the "perspective" in which all the "illusions" of free will is explained first of all exists uniquely at all. I personally don't think so, which is why my view is that all there is are "interacting" incomplete views... without any master view. All there may be are equilibrium points where views have negotiated to get "in tune".

  6. Oct 3, 2011 #5


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    Welcome to PhysicsForums, RawProduce!

    A couple of comments. First, I would agree that we do not know what is going on at a physical level (your comment about the map not being the territory).

    But your comment about determinism does not follow. Evidence of indeterminism (random results) does not lead to the conclusion there is determinism (but we are simply ignorant of the root cause). There need not be any root cause.

    As has been pointed out in the other thread, the measurement issue does NOT lead to the HUP.
  7. Oct 3, 2011 #6

    Ken G

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    I'd add two points:
    Determinism and randomness are elements of theories that we use to describe reality. I consider it naive to imagine that reality could be either of those, nor is the precision of any measurement sufficient to establish either, so the impact on free will is inconclusive (note that neither randomness nor determinism allows for free will as we normally imagine it, so as soon as we assert those are the only alternatives, we have chosen to regard free will as an illusion prior to any inquiry on the topic).

    Also, there are other meanings of "free will", along the lines of "uncoerced choice", that are ambivalent to the fundamental physics description. If we are allowed to make a choice that is "natural" to us, rather than constrained by someone or something else, regardless of how we imagine natural is determined, then we may say that our will is "free" in that situation.
  8. Oct 3, 2011 #7
    One of the shortest fragments of Heraclitus as translated by Martin Heidegger says something like : "approaching".
    Maybe the whole destiny of the damn species is to eternally get closer without being able to grasp the thing in itself.
    Beautiful, but a real tragedy.
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  9. Oct 3, 2011 #8

    Ken G

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    Is that really such a tragedy? I think the complete stripping of mystery would be the worse tragedy, frankly. Each discovery is supposed to open up a wider frontier, not a narrower one, and not a vanishing one.
  10. Oct 4, 2011 #9
    Have you read this?: Misconception of the Heisenberg Uncertainty Principle by ZapperZ, one of the Mentors here at PF.

    Actually, objective reality is generally pretty predictable. So are the statistical results of quantum experiments involving large numbers of trials and multiple runs. It's generally just the results of individual measurements that are unpredictable, some of which is due to the inability to control initial conditions and detections beyond a certain accuracy because of technological constraints. However, QM, unlike classical physics, also incorporates a limiting factor which doesn't have to do with technological limitations, the assumption of the existence of a fundamental quantum of action. But, as DrC indicated, that doesn't have anything to do with whether nature is evolving deterministically or indeterministically.

    This seems like a good assumption. Of course the problem is that there's no way to precisely know just how the maps might approximate the territory, since we have no direct sensory apprehension of the territory (insofar as the term "territory" refers to objects , events, and interactions that underly instrumental behavior and which are inaccessible wrt our direct or augmented sensory apprehension).

    Actually, from our perspective, 'systems' generally seem to evolve deterministically, ie., somewhat predictably, even though precise predictions of individual events are problematic. So, there's an apparent 'deterministic' order wrt the evolution of 'reality'. Things don't, in general, seem to be happening willy nilly randomly.

    Our perception/apprehension of a generally predictable regularity wrt the evolution of objective (ie., publically agreed upon and empirically testable) reality, wrt which physical science is the most stringent adherent (so I don't understand your distinction between objective and scientific senses), has both concrete and philosophical implications. Pretty much all of our endeavors (scientific, social, personal, whatever) are based on the expectation of a more or less predictable evolution of events and the associated assumption that our world is causally deterministic.

    The logical conclusion, given the evidence, is that there is no free will (in the sense that I think you mean it). Of course, as has been pointed out by Ken G, there are different definitions of the term "free will" that are compatible with determinism. But none of this should impact the experimental facts or the interpretation of experimental results.

    The 'observers' of quantum phenomena are the instruments which amplify those phenomena to a level that's amenable to our direct sensory apprehension. Considerations of human free will have nothing to do with it. Bell's theorem and free will are sometimes connected. But again, free will has nothing to do with the truth of Bell's theorem. Local realistic hidden variable theories of quantum entanglement per Bell's formulation are ruled out whether or not humans have free will, and whether or not our universe is exclusively local and evolving deterministically.

    Back to your point. Because of the way you phrased your first statement, I'd have to disagree with it. After all, science, and the body of knowledge produced by it, is part of reality. But since you seem to be saying that the HUP doesn't imply anything wrt free will and determinism, then I agree with that.

    EDIT: On the other hand, since the HUP specifies a quantitative relationship, limited by h, between quantum conjugate variables, and since this relationship is well supported experimentally, then this might be taken as evidence supporting the assumption of determinism (and against free will).
    Last edited: Oct 4, 2011
  11. Oct 4, 2011 #10
    Do you know Faust ?
    The eventual disclosure of truth about the nature of matter cannot tell us anything about the way we must live or deal with each other, the shape of humanity's future or the meaning of history. The real mystery of being will never vanish.
    It's the origin of the clear demarcation between the domain of science and the wider realm of life and thinking. Thought could take us far beyond our factual determinations.
    And don't take it for a basic endorsement of "free will".
  12. Oct 4, 2011 #11


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    I prefer to think of free will as a choice between measurement systems.
  13. Oct 4, 2011 #12

    Ken G

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    Yes, exactly.
    I agree with all that (except the shape of humanity's future part-- that could easily be changed by disclosure of truth, for good or ill).
    There are more things in heaven and earth, Horatio, than are dreamt of in your philosophy.
  14. Oct 4, 2011 #13


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    The topic here is philosophy, not physics, and accordingly belongs in our Philosophy forum.

    http://https://www.physicsforums.com/forumdisplay.php?f=112 [Broken]

    If the OP or someone else wants to re-start the discussion there, please take note of the "rules" sticky post at the top of that forum.
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