In this blog post, Elizier Yudkowsky criticizes Chalmers' idea of "p-zombies" - that is, a physically identical version of the universe in which all the same physical actions and events happen but consciousness and inner experience is somehow "missing." He emphasizes that he's not responding to a practical assertion that a p-zombie is a plausible thing within the real universe, but the "logical possibility" of such a thing, and the purported argument that p-zombies being "possible" means that materialism is definitely false.

Yudkowsky's argument (as I understand it) is not so much a direct refutation of Chalmers' premise or logic as it is a meta-argument that Chalmers cannot have soundly arrived at the conclusion he claims. Essentially,

  1. P-zombies being possible implies that "consciousness" (deliberately leaving open what exactly that means) is epiphenomenal. (And Chalmers seems to explicitly agree with this bit)
  2. But an epiphenomenon cannot cause Chalmers to write books and make arguments to other people about consciousness, since these are physical actions.
  3. Therefore, what Chalmers is calling "consciousness" cannot be the cause of him talking about consciousness.
  4. Chalmers' beliefs about "consciousness" would therefore be unfounded ("miraculous") even in the event they were true.
  5. However, in the event they were true, there must be a physical reason for Chalmers to write papers and make arguments, separate from his "consciousness."
  6. This physical reason is what materialists (including Yudkowsky) mean when they say "consciousness."
  7. Looking past his incredulity, he concludes that asserting even the possibility of a Zombie World entails:
    1. a physical cause to which all conscious actions and behaviours can be attributed, i.e. materialism
    2. that the non-physical properties Chalmers wanted in the first place are not only superfluous, but impossible to justifiably believe in

Has anyone, particularly Chalmers himself, responded to this idea? My understanding was that while materialism/computationalism is a popular position on the nature of mind, most people who disagree with it do not go so far as to say there is a causally effacious soul, and that in-between position doesn't seem viable in light of this argument. As mentioned, Chalmers seems to explicitly agree with some very weird implications of the idea, like that the "outer Chalmers"' actions not actually being caused in any sense by the "inner Chalmers" - does he, or anyone else, elaborate on how that possibility is not as deranged as Yudkowsky suggests?

  • Seems to me that a similar argument can be made against Yudkowsky. If materialism is true, then Yudkowsky is not making his arguments because materialism is true; rather, he is making the argument because the various physical events in his brain compel him to make the argument. Commented Jul 24, 2023 at 22:18
  • @DavidGudeman A materialist wouldn't say they are being "compelled" by physical events in the brain, they would say that they are the physical events in the brain.
    – causative
    Commented Jul 25, 2023 at 9:08
  • So in the materialist view, what they say about consciousness is caused by the physical events that are consciousness. This means there is a causal link between the words coming out of their mouth and the subject of those words. In contrast, Chalmers thinks there is no such causal link, and it's pure coincidence if the words coming out of his mouth have anything to do with his actual consciousness.
    – causative
    Commented Jul 25, 2023 at 9:11
  • @causative, what difference does it make? A causal link has nothing to do with a logical link. Commented Jul 25, 2023 at 10:46
  • @DavidGudeman It does for any empirical statement you want to make. If you see a dog, and then say you saw a dog, that's a casual link between the object you saw and the words out of your mouth. The physical dog caused photons to enter your eyes, which caused a change in your mental state, which caused you to remember having seen the dog, which caused you to say you saw the dog. If that casual link between the dog and the words you spoke were not there, you would be lying or hallucinating.
    – causative
    Commented Jul 25, 2023 at 14:30

1 Answer 1


David Chalmers himself has responded to criticisms similar to Yudkowsky's in various forums. The argument you've outlined hinges on the idea that consciousness, if it were an epiphenomenon, should not influence physical actions like writing books or giving speeches. It suggests that if p-zombies are logically possible, then consciousness must be an epiphenomenon, and therefore, it should not have any causal power.

Chalmers agrees that consciousness, in this framework, does not have any causal power over the physical world. However, he might argue that consciousness is not entirely causally inert. In his book "The Conscious Mind," Chalmers introduces the idea of "double-aspect theory of information," where information has both a physical and a phenomenal aspect. This is not to say that the phenomenal aspect influences the physical aspect, but rather that there's a kind of parallelism or correlation. When certain physical events happen (like neurons firing in certain patterns), there are corresponding conscious experiences.

This is Chalmers' way of reconciling the "logical possibility" of p-zombies with the fact that we do, in fact, talk about consciousness and write books about it. He's not claiming that our consciousness "causes" us to write these books in the physical sense. Rather, he would argue that there's a certain kind of information processing happening in our brains that is correlated with our conscious experiences. When we write about consciousness, we're responding to these physical processes, not the consciousness per se.

Chalmers' argument does to some extent rely on what could be considered a mysterious or unexplained correlation, which is why it is often criticized by stricter physicalists. However, it's important to note that Chalmers is not asserting the existence of p-zombies in our world, but is merely using them as a thought experiment to illustrate what he sees as a gap in physicalist theories of mind.

  • While this looks like a good summary of his view, I'm not seeing how it is a response specifically to the issues of absurdity or redundancy Yudkowsky brings up, it's effectively reiterating the points he's attributed in the OP
    – redroid
    Commented Jul 28, 2023 at 10:05

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