The Simple Flaw in Chalmers’ Argument for the Hard Problem of Consciousness

Important news about your Zombie twin and consciousness outside of physics

David Chalmers’ “Hard Problem of Consciousness” is a highly referenced theory in the philosophy of mind. He argues (in his 1996 book “The Conscious Mind”, and much more) that one aspect of consciousness - “phenomenal consciousness” (aka “conscious experience”) - cannot be explained by physical laws. The explanation for “what it is like” to experience a sensation must come from somewhere outside of physics. Chalmers’ argument is often used to discredit materialism/physicalism (the idea that physics can explain everything, if we knew enough physics) and instead to support various dualist approaches (the idea that there are things that will never be explained solely by physics, and will only be explained by adding something else).

Unfortunately, Chalmers’ argument has a simple and fatal flaw. The fatal flaw is: Chalmers assumes what he intends to prove. It’s circular reasoning. Specifically, he defines “phenomenal consciousness" in such a way that his conclusion is tautologically true. “Phenomenal consciousness” is defined by Chalmers as what it’s like to experience or feel a sensation, but only in such a manner that it does not have any effect on one’s physical or behavioral self. By definition, not a single molecule in the person can be altered by such a “conscious experience”. If a single molecule changes, then this is a different aspect of consciousness, which Chalmers calls “psychological consciousness”. “Psychological consciousness” is amenable to physical explanation, but “phenomenal consciousness” is not. You can see where this is leading. Chalmers defines something outside of physics, assumes its existence outside of physics, and then proves that this something exists outside of physics. This is his proof that there is an aspect of consciousness existing outside of physics: assume it to exist, and then it exists. This is circular reasoning.

Let’s be specific. Probably the most famous aspect of Chalmers’ argument is his “Zombie twin” (p. 94, The Conscious Mind). Chalmers describes the following: “let us consider my zombie twin. This creature is molecule for molecule identical to me, and identical in all the low-level properties postulated by a completed physics, but he lacks conscious experience entirely.” Both Chalmers and his Zombie twin then observe the same tree in physically identical environments, down to the last molecule. The Zombie twin and Chalmers both have identical physical responses to the tree, since they have identical psychological consciousnesses. However, Chalmers has a conscious experience of the tree, and the Zombie does not. According to the argument, it is conceivable that the Zombie twin and Chalmers could have identical physical existences, while having different extra-physical conscious experiences. And by the argument, the fact that this is a conceivable scenario means conscious experience cannot be explained by physics alone - because the conscious experiences are different even though the physics are identical.

Of course, this scenario is only conceivable because Chalmers has defined conscious experience to be outside of physics. If Chalmers had defined conscious experience as having any impact whatsoever on the person’s physical self, the argument would collapse. If conscious experience has any physical impact, then the Zombie twin and Chalmers would not have identical physical responses and the conclusion could not be drawn. Only using Chalmers’ assumption, that conscious experience by definition exists outside of physics, does one conceive that a Zombie would be physically identical to Chalmers but would have some extra-physical difference. I.e., Chalmers assumes something outside of physics, and then uses it to prove that something is outside of physics.

Let’s illustrate this circular reasoning another way. Our preconceptions around consciousness are pretty loaded, so it can be useful to consider this whole argument using different terminology. I will posit the existence of auras around peoples’ bodies. These auras are invisible. The auras have no impact whatsoever on the person or the world around them. They are not measurable, and they do not interact with the physics of the world. However, I do have a personal intuition that my aura exists, and in fact many people I know also share that intuition about their own auras. Now, imagine I have a Zombie twin. This Zombie is molecule-for-molecule identical to me. Can you also imagine it is possible for me to have an aura but my identical Zombie does not? Yes, you can. This proves that auras cannot be explained by physics (because two physically identical entities differ on their aura-ness), and consequently that materialism/physicalism is false.

That was a circular argument. I defined and then assumed the existence of something outside of physics. I then used that to prove the existence of something outside of physics.

One likely critique of my aura example is that most people do not in fact have intuitions about their auras, whereas people really do have intuitions about the existence of their conscious experiences. Chalmers makes this argument repeatedly. However, this is a false argument. Conscious experience by Chalmers’ definition cannot give rise to any intuition. If it were to give rise to such an intuition, this would be a physical/behavioral change in us, which by definition cannot result from conscious experience. The fact that we say we have such an intuition means that it must be about psychological consciousness (which is the only consciousness that can give rise to behaviors like intuition). It cannot be an intuition about conscious experience. We simply cannot report anything about conscious experience, by its definition.

Another possible critique of my thesis is that I have mis-defined Chalmers’ phenomenal consciousness. I have set a strawman, easy to discredit. This is a difficult critique to answer, because Chalmers does not unambiguously define phenomenal consciousness in his 1996 book. The definition I use comes first from pages 10-12, where he defines it contra psychological consciousness, and second where he uses it in his Zombie argument, as I quote above from page 94. According to these descriptions, any mental aspect that would give rise to physical or behavioral change of any kind is psychological consciousness, not phenomenal consciousness. The Zombie argument only holds if not a single molecule changes, so phenomenal consciousness must be defined as outside of physics. Chalmers is fairly consistent with this definition, for example, throughout section 3 of the book. The main exception is when Chalmers states that phenomenal consciousness is “what it is like” to experience or feel something. Typically, to “feel” something would imply some form of physical or behavioral change. To reconcile this seeming contradiction, one must place any physical or behavioral change due to “what it is like” or “feeling” as in the realm of psychological consciousness, and only non-physicalist properties of “feeling” as in the realm of phenomenal consciousness. What results is that phenomenal consciousness is outside of physics.

It is worth noting briefly what I am not claiming. I am not arguing against the existence of phenomenal consciousness. My point is that Chalmers’ argument is logically flawed by being circular: he defines and then assumes a concept which is tautological with his conclusion. In some future, if phenomenal consciousness is found to exist, Chalmers’ argument would still be tautological. My points also do not support or detract from materialism, nor do they support or detract from dualism. One or the other of these ideas may yet prove to be true, but we shouldn’t be using Chalmers’ argument to make the case.

To summarize, Chalmers’ argument for the “hard problem” of consciousness is circular. He defines something outside of physics, and then uses it to prove that it is outside of physics. Because of this flaw, we really should refrain from using his argument to critique materialism/physicalism and to support dualism.