The causal principle states that everything must have a cause. William Lane Craig argues that even in the cases of subatomic events in QM, there are certain necessary conditions that produce an effect, even if they don’t sufficiently produce an effect.

My concern is deeper than this. The question I have is how can we rule out the notion of measurements affecting a system in such a way that it only appears to create effects that don’t have sufficient causes? If this was true, is this the same or different from superdeterminism? If this was true, would it be a local or non-local hidden variable theory?

Interestingly, I found the same concern in an SEP article here. As quoted,

It is true that, given Heisenberg’s principle of uncertainty, we cannot precisely predict individual subatomic events. What is debated is whether this inability to predict is due to the absence of sufficient causal conditions, or whether it is merely a result of the fact that any attempt to precisely measure these events alters their status. The very introduction of the observer into the arena so affects what is observed that it gives the appearance that effects occur without sufficient or determining causes. However, we have no way of knowing what is happening without introducing observers into the situation and the changes they bring. In the above example, we simply are unable to discern the intermediate states of the electron’s existence apart from introducing conditions of observation. When Heisenberg’s indeterminacy is understood as describing not simply the events themselves but these events relative to our knowledge of the events, the Causal Principle still holds and can still be applied to the initial singularity, although we cannot expect to achieve any kind of determinate predictability about what occurs in specific cases on the sub-atomic level given the cause.

  • You write "local or non-local hidden variable" similar you did in your previous question on Bell's theorem. Do you mix up the term with "local, hidden-variable theory"? Note: The theory is a local theory, not the variable a local variable.
    – Jo Wehler
    Nov 8, 2023 at 13:27
  • @JoWehler Yes, that is what I meant. I edited it, thanks for the correction.
    – user62907
    Nov 8, 2023 at 13:29
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    How can we rule out Cartesian demon affecting our minds in such a way that it only appears to create effects we take to observe? The answer is we can't. Such concerns are called skeptical concerns and the response to all of them is the same: idle hypotheticals do not warrant consideration. Until we have tangible reasons to consider skeptical scenarios they are to be dismissed out of hand. The SEP quote brings up Heisenberg's early interpretation of the uncertainty principle that he walked away from and physicists now consider obsolete.
    – Conifold
    Nov 8, 2023 at 13:31
  • @Conifold Quantum mechanics is to my knowledge the only field where measurements do, regardless of whatever your interpretation is, impact the system in a significant way. Even in the Copenhagen interpretation that posits inherent randomness and thus a clear violation of the causal principle, the concept of a wave function collapse exists in that the measurement changes the system. As such, it seems that there is more tangible reason here to not rule out what was proposed compared to other more skeptical theses such as a Cartesian demon.
    – user62907
    Nov 8, 2023 at 13:54
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    @thinkingman Actually, there are many cases where a measurement can affect the measured variable, well beyond QM. For instance, when measuring the temperature of a solution, one has to dip a thermometer into it. Doing so might have a (tiny) effect on the temperature to be measured.
    – Olivier5
    Nov 8, 2023 at 15:48


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