For the sake of discussion, let's grant the validity of reductive materialism. Moreover, let's entertain the notion that our universe is just one among an infinite (or significantly vast) number of universes, constituting a multiverse.

Quantum Mechanics, General Relativity, and the Standard Model represent our most advanced frameworks for understanding reality at present. However, as far as my understanding extends, they do not address how brain states translate into conscious subjective experiences or qualia ("what it is like to be something", what things "feel like").

Therefore, to achieve a comprehensive theory of reality capable of accommodating qualia, we require an additional set of "psychophysical laws." These laws would establish a correspondence between brain states (or physical states, if we want to leave open the possibility of physical structures other than brains, such as robots, having consciousness) and conscious experiences.

For instance, such laws would determine how my current brain activity correlates with my conscious perception of viewing the screen of my laptop, including the distribution of colors displayed by my browser according to the design of the Philosophy Stack Exchange site as I type this message. As far as I'm aware, there is nothing in Quantum Mechanics or the Standard Model predicting or prescribing that this is the conscious experience I ought to have under these specific circumstances.

With this in mind, I argue that it's within the realm of epistemic possibility to conceive of an alternate universe (let's call it B) resembling ours (let's call it A), both being for all practical purposes identical to each other, except for the fact that each one is governed by a different set of psychophysical laws. In universe A, a brain state X may correspond to the conscious experience of "seeing my arm," while in universe B, the same brain state X might evoke the conscious sensation of "seeing static," "seeing white noise," "tasting chocolate," "feeling heat," or even entail no conscious experience at all (see p-zombie).

According to reductive materialism, is it within the realms of epistemic or metaphysical possibility to entertain a scenario akin to the one I propose?

Could two universes within a multiverse be virtually identical except for their divergent psychophysical laws, delineating unique mappings from physical states to conscious subjective experiences?

Note: I'm borrowing the concept of psychophysical laws from a paper I referenced in my previous question, Does psychophysical harmony strongly point toward theism?


Pictorial illustration of the concept of psychophysical laws:

enter image description here

(Taken from: https://youtu.be/uk-2FdSVy10?t=821)


3 Answers 3


Short answer

No. You are mistaken about what reductive materialism is. If you postulate reductive materialism, then mind is just an aspect of matter. There is an identity between some aspect of matter, and mind. There are no "Psycho-physical laws" in reductive materialism, just an identity relation. We just do not yet understand how the laws we already HAVE, generate consciousness. But no NEW laws are needed.

Longer answer

Maybe. Because we don't know how consciousness occurs the Identity Theory assumption of Reductive Materialism may not be valid in this universe. Emergent physicalism is another non-spiritual possibility. Emergence brings in the sorts of phyco-physical laws you reference. AND -- if one is postulating a complex enough multiverse, SOME universes in it might have reductive materialism true of them, some might have a different identity version of reductive materialism, and some might have varying kinds of emergent physicalism and different psycho-physical laws, etc.

With this broad conception of a multiverse, then THIS universe could have a reductionist identity relationship, while other universes are very different.


It's not a bad question, but it isn't currently answerable, because it relies too much on concepts that are purely speculative. Yes, IF reductive materialism is true, then there must be some materially grounded mapping between physical states and mental ones. But without knowing any of the details of how that would work, or what it would rely on, there's no grounds for us to rule one way or the other on the question at issue, (particularly since we're also relying on the also highly speculative concept of the multiverse).

It's tempting to see this inability as an argument against reductive materialism, but while I'm in sympathy with that instinct, I don't think that works either. The thought experiment exposes how much we still don't know about the connection between the mental and the physical, but it's not capable of allowing us to draw any other solid conclusions.


However, as far as my understanding extends, they do not address how brain states translate into conscious subjective experiences or qualia ("what it is like to be something", what things "feel like").

Or maybe they do? Imagine a neural network, like ChatGPT. It has subjective experience -- this we know because it learns certain ideas from that experience, and it acts (it communicates) according to those ideas. In doing so it also makes its own choices, so it has agency. Now, can you imagine that being ChatGPT feels like being something? And if it does, then how do you know that that something (the way being ChatGPT feels) is substantially different from how being yourself feels to you?

We don't require an additional set of "psychophysical laws" to explain the subjective experience of ChatGPT -- nor do we have reasons to doubt that it has one. What makes your brain any different? After all, it's a neural network too.

UPDATE: You can argue that ChatGPT is not conscious of its subjective experience -- and I would agree, most likely it is not. However, being conscious -- of yourself and your experience -- might refer to our ability to visualize a simulation of the world and to model ourselves as part of that simulation.1 And this computers can do as well -- any realistic computer game is an example of such a simulation (though, again, I really doubt that ChatGPT has spontaneously developed this capability).

Now what sets us humans apart from both ChatGPT and computers running simulations is our capacity to piece one together by ourselves and, by doing so, to become conscious.

1 It appears that the mysterious Ancient Greek's logos was, originally, their term for one's simulation of reality. The word itself is a derivative of the proto-Hellenic lego, which means "to assemble". It is also a relative of the Tocharian luk, which means "to gather with eyes", and of the English look. The mostly forgotten difference between seeing and looking could then be the same as the difference between hearing and listening -- that is, between the sensory perception and making sense out of it.

  • @Mark -- you read my mind. I just updated my answer to address your comment. Commented Feb 21 at 22:23
  • @Mark -- by the way, I think Lex nailed it: ChatGPT learned to fake consciousness. But then again so can we, humans. We all have the capacity to develop consciousness but, failing that, we can learn to fake it rather convincingly. Until, that is, millions of seemingly rational people decide to, first, vote for Hitler and then die for him -- that's when their imitation game becomes less convincing. Commented Feb 22 at 0:52
  • "to piece one together by ourselves" - our brain structure is something we're born with (and that may change over time) as a result of billions of years of evolution, and we build a model of reality based on sensory input. The structure of an AI model is something it is created with (and it may change over time) as a result of lots of work by AI researchers, and it builds a model of reality based on fed-in input. Given the parallels there, that doesn't seem like a differentiating criteria.
    – NotThatGuy
    Commented Feb 22 at 10:24
  • 1
    @YuriZavorotny "we build artificial neural networks and we know what they do" ... which is exactly what we CAN'T say about human minds (at this point in time), so your confident assertions about the inner workings of the human mind seems entirely unjustified. This seems to be a problem with every other person talking about AI: "I don't understand B. But I understand A, and based on that I know A and B work differently" - that's not how comparisons work. You can't compare 2 things when you only understand one of the things. Understanding AI doesn't make you a neuroscience expert.
    – NotThatGuy
    Commented Feb 22 at 21:52

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