What do I mean by a 'transparent' specification? I mean to exclude broad general terms (like 'physical' or 'non-physical') whose extensions might be controversial. This helps us to avoid pointless terminological debates. Note that it's a bit sloppy to argue, "Conceivably a world could be physically just like ours but lack consciousness, therefore physicalism is false," because it is unclear exactly what we are meant to be conceiving: the phrase 'physically just like ours' is too opaque: different people might take it to mean different things. [Plus, its invocation of actuality - 'our world' - technically violates the semantic neutrality requirement.] So, for maximum rigor, it should be replaced by a precise microphysical description P that - without making any explicit reference to qualia - is accepted by the physicalist as true of our world. We can then argue from the conceivability of (P & ~Q) to the precise conclusion that the qualitative properties in Q are not reducible to the properties specified in P, and so must be explicitly added as further primitives to the base facts.
It is important to note the precise conclusion here. It is not that Q is non-physical, or that physicalism is false. It is merely that Q does not reduce to anything included in P. Importantly, none of the premises say anything about whether P exhausts the physical properties. (We chose P so that the physicalist should agree that it does exhaust the physical properties, but that occurs outside of the scope of the argument itself. This is a vital point that I will return to.) So one could, in principle, respond that Q is a primitive "physical" property that doesn't reduce to any of the other ones listed. This "physicalist" will insist that a full specification of the physical base facts P* must include Q as a basic conjunct, in which case (P* & ~Q) will be straightforwardly inconsistent, seeing as how it would be equivalent to ((P & Q) & ~Q) for some P. Clearly, this "physicalist" is completely immune to refutation by the kind of conceivability argument discussed here.
That's fine, except that this is to be a "physicalist" in name only. Once you grant that qualia are primitive, and must be explicitly included in the base facts, that's all the dualist cares to establish. Whether you call these primitive mental facts "physical" or "non-physical" is mere semantics.
The target of the zombie argument is instead the strict physicalist, who refuses to countenance primitive mental properties. He believes that we can fully specify the base facts of the world without any explicit mention of qualia. P alone will suffice for Q, on his view, just as P suffices to fix the macroscopic table and chair facts. But since P (unlike P*) makes no explicit mention of Q, we have some chance of running a conceivability argument against this view, since it looks like (P & ~Q) could be conceivable. It's not a knock-down argument, of course: one could reasonably deny that it really is ideally conceivable at the end of the day. But at least the zombie argument has a chance, unlike in the previous case.
Why am I harping on about this at such length? Well, I think this background can help us diagnose the misunderstanding implicit in Richard Brown's dismissive parody:
I am conceiving of a world that is just like this one in all non-physical respects except that it lacks consciousness. Therefore dualism is false.
This exhibits the same sloppiness exhibited by the sloppy version of the zombie argument discussed at the very start of this post. The difference is that while the zombie argument can (as demonstrated) be made more precise, this parody -- what RB now calls his "zoombie argument" -- cannot.
What's the problem? Well, as before, it's entirely opaque what we are supposed to be conceiving, since there is no uncontested specification of the "non-physical respects" of the world that we can plug in to the argument. I take it Brown wants to plug in the actual non-physical description 'NP', whatever it may be. But dualists and physicalists have wildly differing ideas about what this description will end up looking like. Physicalists presumably think it will be empty (i.e. tautologous: devoid of information), whereas dualists think it will list all the qualia facts Q. Let's consider these two possibilities in turn.
- Suppose NP states nothing (i.e. is tautologous). The argument is then as follows: "It's conceivable that (TAUT & ~Q). Therefore dualism is false." Well, that's clearly invalid. The possibility of ~Q is clearly compatible with dualism!
- Suppose NP just states Q. Then the argument is: "It's conceivable that (Q & ~Q). Therefore dualism is false." But in this case the first premise is transparently false.
So, you see, whichever way we fill out the precise details of the parody argument, it very clearly fails (unlike the original zombie argument which, though controversial, can at least get off the ground, since "P & ~Q" is neither trivial nor trivially false).
You might wonder: if the parody is so atrocious, why would anyone have ever been tempted to take it seriously? I think the answer is just that they haven't fully appreciated how restrictive the form of conceivability inference relied upon by the original zombie argument is. If one assumed that the zombie argument must take the sloppy (opaque) form introduced earlier, then one may well be right to see the parody as being of the same form, and hence undermining that form of argument. I'm happy to grant this: opaque conceivability arguments are no damn good. But - once again - this does nothing to impugn the zombie argument, since it can be stated in a more transparent form (as described*).
* = (Of course, I've really only provided a schema of the argument. The real thing will have the placeholder 'P' replaced by a long, transparent description. But insofar as we have a rough grasp of what P will look like, we can draw tentative conclusions about whether the expanded version of 'P & ~Q' is likely to be conceivable.)
Compare Brown's recent response:
The zoombie world is a COMPLETE non-structural/non-functional duplicate of our world. NP is not just some random list of non-physical properties! It is a complete list of the actual non-physical properties. So, if there are no non-physical qualitative properties in NP then the actual qualitative properties that you and I enjoy are not non-physical properties.
I hope it's clear by now that this is a wildly different form of argument from the zombie argument I've given. Instead of using NP as a mere placeholder for some list of non-physical properties (neutrally and transparently specified), he is explicitly building in its status as "a complete list of the actual non-physical properties". So when he asserts that (NP & ~Q) is conceivable, this is mere shorthand for the same old sloppy, opaque conceivability claim as before (viz., that conceivably, "a world could have all the actual non-physical properties but lack qualia"). In effect, he is (unwittingly) pretending to give a precise, transparent specification by mimicking the superficial form of my argument, when in fact the underlying form and actual content of his argument hasn't changed a bit from the sloppy version.
To recap: a legitimate conceivability argument should begin by providing a transparent, uncontested specification of what is to be conceived. The zombie argument does this, by taking whatever specification 'P' the physicalist likes (which the dualist will not contest). The 'zoombie' parody, by contrast, does not meet this condition. This is indicative of further problems downstream -- and indeed, when we consider the two main candidates for fleshing out 'NP' (namely: TAUT or Q), we immediately see that neither has the faintest hope of grounding a conceivability argument against the dualist. The entire force of the parody argument rests on the opacity of 'NP', and -- unlike the real zombie argument -- it cannot survive being rendered transparent.
[This is all just to elucidate the objection originally stated in a couple of sentences in my 'zombie review'.]