To prove experimentally that dualism is true, the dualist would need to show that:

Let be a person in physical state A at some instant t1 with conscious experience X.

Now, in another instant t2, the same person is again in physical state A, but now has conscious experience B.

This would prove that the mental doesn't depends on the physical, since two exactly physical states entailed different conscious experience.

Would this experiment prove that dualism is true?

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    That's not an experiment. There is no way to measure "physical state" in its entirety, and no way at all to compare "conscious experiences". Dualism, materialism, idealism are not scientific claims that can be proved or disproved experimentally at all, philosophy is not science. They stand or fall on how well they organize our views as a whole, experiments being only a small and inconclusive part of it.
    – Conifold
    Sep 8, 2021 at 20:47
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    @Conifold It is conceivable that, say, a Kardashev II or III civilization could measure and arrange the physical state of a brain down to the atom. They would be limited in this by the uncertainty principle, but it could be possible to get very close to setting up the same state twice.
    – causative
    Sep 8, 2021 at 21:06
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    @Conifold I think I wanted to express a thought experiment. Sep 8, 2021 at 21:25
  • @causative Why stop at atoms? Perhaps, "consciousness" supervenes on some sort of quantum gravity effects in microtubules, as Penrose suggests. And even if they could clone those (disregarding uncertainty) they still can't be sure they got it all the same, unless they have divine omniscience. The point is that experimental setups always make background assumptions and allowances, and those always create loopholes. Experiments can make metaphysical doctrines implausible, given the totality of other beliefs, but they neither decide them on their own, nor conclusively.
    – Conifold
    Sep 8, 2021 at 22:29
  • This is not even a thought experiment, just a rephrasing of (one) definition of dualism.
    – Conifold
    Sep 8, 2021 at 22:31

1 Answer 1


The experiment is incompletely specified. How would you measure the conscious experiences X and B?

Presumably you would have to ask the person what they experienced, and take their answer as fact. But their reporting of a difference in experience is a physical difference; words, noises, are physical events. So we find that the physical consequences of state A were different between times t1 and t2.

This difference in physical consequences could be the result of randomness in the setup of A, or inherent randomness in the laws of physics.

Or it could be the result of some mysterious non-physical influence - some soul guiding the person's behavior.

So, the experiment would still be inconclusive.

It would be more conclusive if you could also trace the entire physical chain of cause and effect that led from state A to the utterance "I experienced X" or "I experienced B." If this chain of cause and effect is in both cases entirely within our understanding of physics, this would be evidence against dualism. On the other hand, if mysterious things happen within this chain of cause and effect that do not fit within our understanding of physics, that could be evidence for dualism - or for a new breakthrough in physics.

  • Why "But their reporting of a difference in experience is a physical difference; " ?The experiments asserts that both persons had the same conscious experience. Sep 8, 2021 at 21:25
  • @Carlitos_30 "The same conscious experience"? But you said at t1 they experienced X and at t2 they experienced B.
    – causative
    Sep 8, 2021 at 21:29
  • Sorry, I meant same physical state, but you comment about reporting a different experience is a 'physical difference': in what ground? Sep 9, 2021 at 2:57
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    @Carlitos_30 If the person says "I experienced X" then he is making sound waves - physical phenomena. If the person says "I experienced B" then he is making different sound waves - different physical phenomena. So the physical result of the experiment must be different; the same initial state A did not always lead to the same physical result.
    – causative
    Sep 9, 2021 at 3:19
  • Good catch! Thanks. Sep 9, 2021 at 3:35

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