He argues that given the universe operates on QFT, we would need to create new physics to account for souls interacting with the physical world. We would need an equation instead of the Dirac equation to explain how the immaterial soul interacts with our brains. Any dualist thoughts on this or did he basically just disproven dualism?

More particularly this arguments seems to target substance dualism.

  • 1
    The problem with his "cheesy Moon" analogy is that in the case of consciousness ("soul") there is quite a lot that "laws of physics underlying everyday life" arguably do not describe or explain, what dualists call the hard problem of consciousness. One can say that they are not meant to do that, and perhaps this is true, but then his premise "the laws of physics underlying everyday life are completely understood" is either false or moot. Of course, dualists still do have to explain the interaction between laws and consciousness.
    – Conifold
    Commented Apr 10, 2020 at 4:36
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    Are you asking about interactive dualism, or are you including philosophical theories which assume consciousness is epiphenomenal in your question? Carroll's argument would seem to only concern the former, not the latter.
    – Hypnosifl
    Commented Apr 10, 2020 at 5:26
  • I'd say he makes an argument against dualism.
    – user20253
    Commented Apr 10, 2020 at 12:44
  • @Dcleve would seem to have a thought in this subject
    – Nick
    Commented Apr 11, 2020 at 15:54

2 Answers 2


Current physics is obviously incomplete or incorrect. It does not predict the existence of consciousness. But we know consciousness exists. Plus we have the known problems of unifying QM and general relativity.

So of course we need new physics because the current physics does not explain the whole world. Consciousness is a part of the world.

  • are you talking about the behavior associated with consciousness such as speech (the 'easy problem'), or subjective experience considered independent of behavior (the 'hard problem')? If the latter there is no obvious reason why physics would ever address this, it is only about predicting measurable changes in the physical world.
    – Hypnosifl
    Commented Apr 10, 2020 at 6:00
  • Well, I'm talking about both. I think the "easy" problems will not be explained without the existence of consciousness... ie: I think consciousness isn't just epiphenomenal. Physics can disprove this by showing that current physics in the brain predicts our social behavior. It has not done anything like this. If consciousness is epiphenomenal, then you're right that physics can't say anything about it. Commented Apr 10, 2020 at 6:06
  • I think you use "consciousness" ambiguously. Physics does not predict what dualists mean by "consciousness", but we do not know that exists. Problems of unifying QM and relativity are arguably moot, as the effects involved likely do not register at the relevant scale. So I do not think either is the problem with Carroll's argument, it is unsound for other reasons.
    – Conifold
    Commented Apr 10, 2020 at 6:07
  • Physics does not predict the existence of "subjective experience". But Hypnosifi is right that there is no reason to expect physics to explain this since it may not have measurable changes. But if physics sticks to that role, then it has nothing to say on the matter if consciousness or souls are epiphenomenal. Commented Apr 10, 2020 at 6:11
  • BTW, I would add that Sean Carroll doesn't have the view that physics merely "makes predictions"... to him physics the more general role of explaining the world. So by his own view on what physics should accomplish, I'd say physics is incomplete. Commented Apr 10, 2020 at 6:18

I'm not a dualist, so bear that in mind, but I can see a couple of immediate logical objections to Carroll's argument.

First — and perhaps this is an unfair critique, even if accurate — Carroll is using a straw-man representation of religious beliefs. The idea of a 'personal' (identity preserving) soul that exists entirely separate from the physical plane is an unsophisticated conceptualization. Yes, it's a common conceptualization among both theists and atheists (which is why this critique may be unfair). But there are other ways of thinking about the biology/consciousness distinction than to treat consciousness as (a) an epiphenomenal byproduct or (b) a disconnected externality, but Carroll doesn't even hint at such. Why not think of consciousness as an emergent property of biology? Why not consider that the consciousness/biology relationship is a two-way street, not a one-way lane starting in biology? Either consideration would make his argument much harder, and as a result much more convincing if he succeeds.

That brings me to the second critique. Although I'll give him bonus point for invoking the Dirac equation, by using it Carroll is implying that the soul (or whatever) has to operate directly on electrons. This is that one-way lane approach: Carrol presumes that any 'spiritual' influence has to start deep down in the basic physics and biology of the brain and work its way up to influence consciousness. But it's well-known that the conscious mind can influence biology: people can slow their breathing or their pulse by act of will; a mere thought or perception can kick off the biological processes of anger, happiness, grief, etc. All we have to do is conceptualize that the 'spiritual' connects at the mental level and works its way down to influence the body, and the Dirac equation no longer applies.

Carroll's argument hinges on the preconception that consciousness is epiphenomenal and fully reducible to biology. That is not something that has been established by science, and without that preconception his argument doesn't have a lot of traction. I mean, I'm sure people will quibble with what I've said — I've just laid out a couple of critiques without building them into a full argument of their own — but I can't personally see a way around these critiques.

  • On the first objection, I think (charitably) he can do that because his main target is afterlife. Assuming something more sophisticated, like property dualism, it is not so easy to explain how the "soul" goes on while its physical carrier disintegrates. Hylomorphists had great difficulty explaining how "substantial forms" can persist without their matter since Aristotle and Aquinas, and modern property dualists, like Chalmers, would probably discard afterlife. Substance dualism is far more compatible with it.
    – Conifold
    Commented Apr 10, 2020 at 20:16
  • @Conifold: Well, I don't know. It seems to me that that the 'afterlife' objection only works because because he ties any concept of a 'soul' to a particular physical body (by presuming that it has to rise to consciousness through fundamental physical principles). If we presume the opposite, that it connects with consciousness and works down to the physical, then it could perfectly well exist across incarnations, merely by connecting to new consciousness. In that case it's not that it 'floats free', but that it starts 'free' and connects intermittently. Commented Apr 11, 2020 at 1:12

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