Can somebody explain to me exactly what David Chalmers' Naturalistic dualism is, because I have heard a lot of conflicting explanations on it?

  • 1
    Heard them where? And what was conflicting in them? We encourage questions with more context because just adding here one more conflicting explanation to the list will hardly make things any better. What exactly are your issues with the Wikipedia explanation, for example?
    – Conifold
    Commented Nov 1, 2019 at 23:08

5 Answers 5


The way I understand it:

While the phenomenal, subjective, first-person, aspects of conscious experience do not logically supervene on the physical facts of our universe (hence dualism), they do so naturally, meaning that in our world, there are apparently certain laws that bridge the gap between the physical and the phenomenological.

Put differently, philosophical zombies are logically possible, but you won't find them in our world.


To supplement Bram28's answer:

I think if you want to fully grasp Chalmers' dualism you need to understand his argument for it. As we read from Schroeter:

Chalmers (1996; 2009) formulates a conceivability argument that seeks to establish that phenomenal properties like being in pain or having a red sensation cannot be identified with any physical or functional properties of the human brain. Chalmers uses his 2D semantic framework to clarify the type of conceivability involved and its connection with metaphysical possibility.

Put as simply as possible, the argument goes like this:

  1. It is a priori conceivable that there could be a world with all of the same microphysical properties as our own, and yet there are no phenomenal experiences. In such a world, there would be beings physically indistinguishable from us that are not phenomenally conscious.
  2. Since such a world is conceivable, it is metaphysically possible.
  3. Therefore, phenomenal states cannot be identified with microphysical states when considering their metaphysical constitution.
  4. Therefore, materialism is false.

This argument is deceptively simple. When read at a surface level, it appears to make some pretty dubious moves. To make this idea plausible or interesting, one has to investigate Chalmers' background theory about the relationship between conceivability, the a priori, and modality. His systematic rationalism and modal epistemology license him to make the leaps in the argument, and in an interesting way.

Hence first point when examining the argument is one of elegance: this argument is a direct application of Chalmers' background rationalist epistemological and metaphysical framework. As a result, the argument arises from a systematic approach to knowledge and meaning. This in itself makes the theory interesting to consider.

When unpacked, there are five moves in the argument:

  1. [Apriori reflection] - Chalmers takes up the commonly-held view that there is no direct logical contradiction in the idea that the physical process that in fact give rise to consciousness might not do so. It is thus conceivable a priori that there might be what are called philosophical zombies. However, the claim is stronger than this. Chalmers takes this logical conceivability to establish an a priori truth. Hence, it is not merely that we are missing details in our physical/physiological theory; even if a perfected physical and physiological theory were forthcoming, no observations are forthcoming that would make it inconceivable that there should be philosophical zombies.

  2. [Epistemic 2D framework] - Here is where Chalmers evokes his background "Two-dimensional Semantics" (2D). Put simply, a 2D semantics is one that assigns meanings to linguistic expressions relative to two possible-worlds parameters (hence the two-dimensional). Chalmers' two parameters are "epistemic possibility" on the one hand, and "metaphysicaly possibility", on the other. The epistemic parameter codifies what is conceivable, and the metaphysical parameter codifies what is metaphysically possible. The basic idea is that we interpret the a priori coherence of philosophical zombies derived in [Apriori reflection] by the semantics: there is an "epistemically-possible" world in which it is true that philosophical zombies exist. But is coneivability a guide to metaphysical possibility? https://plato.stanford.edu/entries/two-dimensional-semantics/#RatPro

  3. [Modal rationalism] - Chalmers' background theory forges an a priori path from conceivability to metpahysical possibility based simply on the way meaning works. He holds that for every epistemically-possible scenario, there is a corresponding metaphysically-possible world. As Schroeter says:

[Modal rationalism] establishes a systematic link between apriori conceivability and metaphysical possibility at the level of the 2D framework. According to Modal Rationalism, ideal apriori coherence is an accurate guide to genuine metaphysical possibility. So every epistemically possible scenario—a complete description of what the world might be like together with your location within that world—describes a genuine metaphysically possible (centered) world. This general claim plays a crucial role in securing the argument against materialism.

  1. [Semantic Stability] - Some statements are of the sort that their two possible-worlds parameters (epistemic and metaphysical possibility, respectively) converge. In such cases, epistemic conceivability and metaphysical possibility line up. Chalmers thinks that the relevant statements in this argument are semantically stable, so that the bridge from epistemic conceivability to metaphysical truth is forged.

  2. [Materialism] - Chalmers employs a corresponding modal definition of materialism that makes the argument run. If materialism is true, then it is not metaphysically possible for there to be philosophical zombies. Since there is a metaphysically possible world at which there are zombies, materialism is therefore false.

Chalmers does not take this to establish a separate mental substance. Rather, he argues that phenomenal properties cannot be identified with physical properties. His naturalism consists in the fact that he does not need to say that there is any kind of causal influence of a mental substance on a non-mental, physical reality:

The arguments do not lead us to a dualism such as that of Descartes, with a separate realm of mental substance that exerts its own influence on physical processes. The best evidence of contemporary science tells us that the physical world is more or less causally closed: for every physical event, there is a physical sufficient cause. If so, there is no room for a mental "ghost in the machine" to do any extra causal work.

We can see that for Chalmers the objectionable aspect about substance dualism is the burden that it must find a way for the seemingly closed causal system of nature to be influenced by an outside agent. However, the introduction of additional kinds of fundamental laws, laws which would explicitly connect the physical properties and the phenomenal properties, is valid if it does not run afoul of the authority of physics on the causality of nature:

Like the fundamental laws of physics, psychophysical laws are eternal, having existed since the beginning of time. It may be that in the early stages of the universe there was nothing that satisfied the physical antecedents of the laws, and so no consciousness, although this depends on the nature of the laws.

In any case, as the universe developed, it came about that certain physical systems evolved that satisfied the relevant conditions. When these systems came into existence, conscious experience automatically accompanied them by virtue of the laws in question. Given that psychophysical laws exist and are timeless, as naturalistic dualism holds, the evolution of consciousness poses no special problem.

It is evident that one potentially confounding variable here is just how loosely the term "naturalism" is used in philosophy. At this point, it's a question of metaphysics. What underlies what at the fundamental level of reality? If you thought that a commitment of naturalism was that at the ultimate, underlying layer only physical properties would remain, then Chalmers will not qualify. But for Chalmers the qualification for naturalism is weaker. For Chalmers, if we keep peeling back the underlying layers to get to the most fundamental ones, there will be phenomenal properties all the way down. We thus need fundamental laws governing the interaction of physical and phenomenal properties. Despite the fact that there are interactions between these two irreconcilably different types of properties, Chalmers generates all of this within the closed causal system of nature.



Chalmers' naturalistic dualism is a response to his realisation that the Mind-Matter problem is metaphysical. He believes that metaphysics is not a scientific pursuit so recommends naturalistic dualism as a way of avoiding doing any. We would assume that Mind-Matter is undecidable and forget about the pursuit of a fundamental theory. We would settle for a non-reductive theory for which we would ignore the difficult questions and stick to what he calls 'naturalism'.

His dualism is not a theory but a way of avoiding metaphysics. I cannot explain why he considers his idea naturalistic but it is certainly dualism. If dualism is false his theory is not naturalistic. It's a way of setting aside the 'hard' problem while we get on with the easy ones. As such it is a methodology rather than a theory.

As transitionsynthesis says above, the word 'naturalism' is used and abused in all sorts of ways and I'm not sure what Chalmers means by it. Afaik he means 'not metaphysical'.

I'm not sure he still endorses naturalistic dualism. A recent article on Idealism explores metaphysics a little so maybe he hasn't quite given up on philosophy.


Chalmers characterizes his view as naturalistic dualism: naturalistic because he believes mental states are caused by physical systems (such as brains); dualist because he believes mental states are ontologically distinct from and not reducible to physical systems.

Although the article in wikipedia goes on to say that this view could also be characterized by more traditional formulations such as property dualism, I can't say that I agree because minds are not things and as such do not have properties - they are 'ontologically distinct'.


Naturalistic dualism of Chalmers:

  • Naturalistic, i.e: Physical substance e.g: brain, produces mental states.

  • Dualistic, i.e: mental states are Ontologically distinct from, and not reducible to Physical Systems, i.e: Information are distinct from energy and matter.

Information=Mental States.

Chalmers suggests that the dualistic (non-physical) element might be information. Indeed it might. With this idea too, information philosophy completely agrees. Mind/body is a property dualism, not a "substance" dualism, as Descartes thought.

Chalmers says that a "fundamental theory of consciousness" might be based on information. He says that "physical realization is the most common way to think about information embedded in the world, but it is not the only way information can be found. We can also find information realized in our phenomenology." (ibid, p.284)

He is quite correct. Information is neither matter nor energy. It needs matter to be embedded temporarily in the brain. And it needs energy to be communicated.

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