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Interaction free measurement

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  • Interaction free measurement

    Experiments have shown an object in a superposition can be measured without interaction. Essentially, a photon goes through a path and is split by some beam splitters. In one path, it can be absorbed by the object in a superposition. The state of the two detectors at the end can be used to determine the position of the object, even if the photon never interacted with it.

    I apologise for my poor explanation, but please do not ignore this post. I believe these experiments might falsify the Thomistic theory of causality, because a change (the collapse of the object's wavefunction) can occur without any causal interaction.

    I would appreciate your thoughts.

  • #2
    By no means am I a specialist in physics, but this doesn't seem to me to be too different from standard QM objections to PSR or the principle of causality. I think Pruss's, Feser's and Koons's answers could be given here as well. One important thing to keep in mind about those "experiments" is that they are compatible with a broad range of different interpretations. It can be difficult to differentiate our failure to identify a cause, and the actual lack of a cause. There are different analyses of causation that could perhaps make sense of what you describe (e.g. backwards causation? hidden variables? And so on).

    Another very important point is that one can always be an instrumentalist about those matters. Roughly, this means that these experiments may not be telling us anything about "real entities" (including photons and such); they just show and describe empirically adequate hypotheses. Science itself is pretty much silent about the dispute between realism and instrumentalism, and many philosophers of science are instrumentalists. So for an instrumentalist, those experiments may not be describing any real entities at all, they are just confirming certain theoretical frameworks that "work", make good predictions, etc. As such it would not pose a threat to PSR or thomistic views of causality.