After I singlehandedly felled the juggernaut of physicalism with one simple article, the defenders of physicalism decided they needed to refute my devastating takedown1. Chef wrote a response, which I’ll reply to here.
Other than the part about me being wrong, I have no disagreement with the first paragraph.
Bentham of Bentham’s Newsletter wrote an interesting article a while back where he sketches a series of arguments against physicalism, citing Chalmers extensively. I will argue, in this essay, that they are wrong, but very understandably wrong. The arguments are certainly valid; no one can impeach the logical structure of Bentham’s or Chalmers’ arguments.
Next, Chef says
1. A being could be physically identical to me but could not be conscious
2. Two beings that are physically identical must have all physical properties in common
3. Therefore, consciousness is not a physical property.
Setting aside our intuitions about (1) for the moment—I’ve written before about why I don’t find p-zombies possible—fine. The argument is logically valid. But there are some other assumptions being smuggled in here. In reality, if we unpack (1), it looks something like this:
1*. A being that is physically identical to me but could not be conscious is conceivable.
2*. Anything that is conceivable is logically possible.
3*. Therefore, it is logically possible that there could exist a being that is physically identical to me but could not be conscious.
I notably didn’t make this argument, because I think it doesn’t succeeds. Lots of things can be conceived of, yet are nonetheless logically impossible. For example, I have no trouble conceiving of the falsity of fermat’s last theorem — yet it’s logically impossible nonetheless. However, for things like the falsity of fermat’s last theorem, there’s some account of why they’re logically impossible — thus, the physicalist would have to have some similar explanation of why zombies are impossible. I don’t think the explanations succeed, and if none of them do, then that would mean that consciousness is, in fact, non-physical2.
We’ll start by thinking about (1*). I claim that the notion of some object X being conceivable is closely related to vagueness. If I can vaguely imagine something but can’t mentally render it in suitable detail, we don’t want to say I can conceive of it. I can sort of, kind of imagine a world where p & ~p is true. I can imagine the possibility, but I can’t tell you in any detail what such a world would be like, and we don’t want to say I can conceive of it. On the other hand, I can conceive of a purple elephant. I can render it in non-trivial detail in my mind. I can visualize it, I can imagine it having brown eyes and a wrinkly trunk, I can tell you what it might eat—in short, I can (in principle) answer probative questions about my purple elephant, and then no one should doubt that I have truly conceived of it.
This points us to the following definition: we’ll say X is conceivable if there exists a person P who can render a mental model of X in suitable non-trivial detail as to, in principle, be able to answer probative questions about X.
And that, too, points us in the direction of two new questions about conceivability: can a person P reliably report if an object X is conceivable, and is whether P believes X is conceivable related to their logical priors?
In order for the anti-physicalism argument to go through, we need it to be the case that people can reliably perceive and report accurately if an object X is conceivable, and we also need it to be the case that whether P perceives X to be conceivable is independent of P’s logical priors (at least on a rhetorical level, if not logically; you won’t have much luck convincing another person P’ that X is conceivable if you can only conceive of it because you already believe in some other proposition Q that P’ disbelieves).
I claim that these conditions are mutually exclusive.
Proof: suppose for all objects X and all people P, whether P will perceive X as conceivable is independent of P’s logical priors. Then the fact that Chalmers and I disagree on the conceivability of p-zombies is proof that at least one of us is (and maybe both are), in principle, not capable of reliably reporting if X is conceivable. Chalmers would, in order to salvage the anti-physicalism argument, have to further furnish an argument showing that he can reliably and accurately report whether an object X is conceivable.
The reason you can’t conceive of zombies isn’t because of a failure of imagination — instead, it’s because you’re convinced of certain philosophical arguments that seem to render zombies inconceivable. These are analogous to proofs of Fermat’s last theorem — it’s falsity may have been conceivable absent the proof but they aren’t now that there is the proof. Thus, whether or not zombies are conceivable will come down to whether the physicalist can give some successful account of why they’re inconceivable. I, like my buddy Chalmers, maintain that they can’t.
Chef finishes with
Absent a better explanation, I’m sticking with reductive physicalism, and I don’t think I’ll be convinced otherwise by arguments from conceivability. Or, at the very least, a successful argument would have to be substantially more complicated than the standard conceivability account of p-zombies.
The problem is physicalism is full of holes. Is there anything else in the universe, any other physical object, to which anything like the knowledge argument could apply, much less the combination of the form and structure, zombie, knowledge, and all the other arguments presented in my article. No, consciousness is unique in this regard! Trying to explain consciousness using purely structural and functional explanations is a doomed endeavor — for nothing about what something does will tell you ever what it’s like to be that thing. It’s positing mystery as an answer to an insoluble problem — we have upwards of seven converging argument each pointing away from it. Would this really be true of the correct theory?
Only one person did this
I later noticed that Chef also used the example of Fermat’s last theorem. Total coincidence! I guess consciousness just makes us all think of Fermat.
Interesting points. I will respond in full at some point. Funny that we both went to Fermat's last theorem! Great minds think alike? My first thought is related to this:
>The reason you can’t conceive of zombies isn’t because of a failure of imagination — instead, it’s because you’re convinced of certain philosophical arguments that seem to render zombies inconceivable. These are analogous to proofs of Fermat’s last theorem — it’s falsity may have been conceivable absent the proof but they aren’t now that there is the proof.
I claim that even though there is now a proof, the fact that I don't have the faintest idea how it works means I can still now conceive of counterexamples (or at least I think I can), but that doesn't mean counterexamples are really possible. In principle, if we suppose a convincing physical account of consciousness, if it exists, must be roughly as complex as the proof of FLT, it's reasonable to think that no matter how correct it is, there'd still be a cognitive gap for zombies to sneak through. I.e. even if physicalism were correct, I think the same arguments against physicalism would seem equally convincing. But this all speaks more to our cognitive limitations than any objective truth imo.