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Possibility of Zombies

et cetera
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Posted 05/11/09 - 05:06 PM: Subject: Possibility of Zombies	#1
A P-zombie is logically possible iff it is conceivable and would not have contradictory properties. Why do you think that the concept of a p-zombie is not self-contradictory? The identity theorist is claiming that brain states are what is referred to as "consciousness". By that logic, if we posit that there is a humanoid who has all the same behaviors and neurophysiology as you or me, how would it be possible for this humanoid to lack consciousness? By just assuming that a p-zombie is a logical possibility have you not already assumed along with it that mental properties are distinct from physical properties? Is you argument intended to reiterate what would follow if such were a possibility? Why should I even indulge that such a controversial claim be true? Also, welcome to PF. Edited by et cetera on 05/11/09 - 05:14 PM
Any necessary truth, whether a priori or a posteriori, could not have turned out otherwise. -- Saul Kripke Meaning is what essence becomes when it is divorced from the object of reference and wedded to the word. -- Quine A possible world is given by the descriptive conditions we associate with it - Kripke

davidchalmers
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1 of 1 people found this post helpful Posted 05/15/09 - 05:43 AM:	#2
Remember that one doesn't just assert that zombies are possible. In effect it comes fro two premises -- zombies are conceivable (in a certain sense), conceivability (in that sense) implies possibility (in a certain sense). Now, of course identity theorists think that consciousness is physical. But they don't usually think that this identity is a priori -- they think it is something we discover empirically. So believing in the identity is compatible with believing that it is conceivable that the identity is false -- in the (relevant) sense where P is conceivable iff P is not ruled out a priori. For the same reason, being an identity theorist is quite compatible with accepting the conceivability of zombies -- many identity theorists do (as do the majority of philosophers, as far as I can tell). Instead the step they'll reject is the step from conceivability to metaphysical possibility. That raises a lot of issues, but the step itself rests on quite general philosophical support, and doesn't require any assumptions about consciousness per se. See my paper "Does Conceivability Entail Possibility" for more on that step, and "Consciousness and its Place in Nature" for the problems involved in views that deny even the conceivability of zombies.

et cetera
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Posted 05/17/09 - 06:18 PM:	#3
davidchalmers wrote: Remember that one doesn't just assert that zombies are possible. In effect it comes fro two premises -- zombies are conceivable (in a certain sense), conceivability (in that sense) implies possibility (in a certain sense). I am familiar with the literature. But it seems you have yet to address my concern with the statement "zombies are logically possible". A zombie is logically possible iff it is conceivable and not contradictory. This is the definition I was taught. It seems reasonable that a round square is conceivable but not imaginable and this alone would not imply that such a thing is a logical possibility. In fact, any further examination into the rigorousness of geometrical proof would show is that such a possibility would imply that we could posit a geometrical object that has contradictory properties. I am sure that this is not a fair question to ask, but does everything follow because a round square is conceivable? Is it known a-priori that a p-zombie is not self contradictory? Maybe we have intuitions. Intuitions aside, what knowledge would we need to be able to make the claim that a p-zombie is a logical possibility? I would presume that we would have to know that a human could exist and function normally while lacking consciousness. You don't know this, I don't know this, I don't know the opposite to be true as well. I might have what I feel to be good scientific reason to think otherwise but that is no matter. What matters is that neither of us know enough about what consciousness is to presume that we can make definitive inferential claims about it. So believing in the identity is compatible with believing that it is conceivable that the identity is false Not necessarily. I can think of a situation in which X's belief that P is true is not compatible with X believing that it is possible that P is false. Specifically within the scope of the former belief. I think your point is to say that the possibility of the identity theory being true is compatible with the possibility of the identity theory being false. I agree, but only in the skeptical and broad use of the word "possible". For the same reason, being an identity theorist is quite compatible with accepting the conceivability of zombies -- many identity theorists do (as do the majority of philosophers, as far as I can tell). Still there is no reason why any identity theorist who claims that physicalism is true must concede that it is logically possible that physicalism is false. Lets just presume they are head strong. If at least one of our premises is that physicalism is true then physicalism is a neccessary truth whereas any possible truths would then be defined by the syntax and semantics of the given formalism, theoretical framework, schema, etc. In that case, a p-zombie would not be a possibility. Since the issue lacks any decisive proof it really boils down to taste. Specifically insofar as we implicitly presume that it is either not contradictory for a fully functioning human to be devoid of consciousness or that it is contradictory for a fully functioning human to be devoid of consciousness. Which one is correct? I dunno. Edited by et cetera on 05/18/09 - 11:06 PM
Any necessary truth, whether a priori or a posteriori, could not have turned out otherwise. -- Saul Kripke Meaning is what essence becomes when it is divorced from the object of reference and wedded to the word. -- Quine A possible world is given by the descriptive conditions we associate with it - Kripke

vuic
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Posted 07/11/09 - 04:06 AM:	#4
"davidchalmers" wrote: Remember that one doesn't just assert that zombies are possible. In effect it comes fro two premises -- zombies are conceivable (in a certain sense), conceivability (in that sense) implies possibility (in a certain sense). I think intuitions are pretty much worthless in the philosophy of mind or anywhere else for that matter, because the range of situations conceivable by us is surely not bound by natural laws, so conceivability cannot tell us anything about natural phenomena.

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Posted 07/13/09 - 09:40 AM:	#5
vuic wrote: I think intuitions are pretty much worthless in the philosophy of mind or anywhere else for that matter, because the range of situations conceivable by us is surely not bound by natural laws, so conceivability cannot tell us anything about natural phenomena. I agree with you entirely. I have separated possibility into logically possible, physically possible, and conceivably possible. Conceivably possible doesn't necessarily entail logically possible or physically possible. One usually thinks that if its conceivably possible, then it should be logically possible, but I beleive sometimes people conceive of hypotheticals that have nested logical contradictions. For instance, I am a hard determinist, and think that all this talk of possible worlds where I do things other than what I actually have done is all a bunch of hooey. We do what we do, and could never have done otherwise because the that would entail a change in the physical conditions of the universe such that only that different result occurs but everything else is the same. I beleive that entails logical contradictions if we could fully see the chain of physical events. The universe is the way it is because any change would entail logical contradictions.

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Posted 07/15/09 - 04:49 AM:	#6
To illustrate the difficulties with intuition let me refer to Nagel's convoluted argument in his "What is it like to be a bat?" Nagel says it would not help if you were to try to imagine what it would be like for you to use echolocation etc. because however hard you try you still could not know what is it like to be a bat for a bat. Let us grant that the expression "there is something that it is like to be a bat (an organism)" makes sense (pace those who argue it doesn't). Now I think it can be shown that the difficulty with Nagel's argument is that it asks us to do something that involves a logical contradiction. To really know what is it like to be a bat, it is not enough to imagine the kind of experience YOU would have if you had the experiences of a bat. Instead, to know that you must TURN INTO a bat, but you cannot do that because your mind is essentially that of a human being. Perhaps you can make sense of the doctrine of transmigration of souls, but that only shows you can imagine what it would be like for YOU to have the experiences of some (non-human) animals. However,according to Nagel, that is not enough to conceive what is it like to be another organism. But note that once "you" turned into a bat, you ceased to be yourself because the conditions of your personal identity collapse. Once "you" are a bat, "you" should possess the same background knowledge of the world a bat has, no more and no less than that. But then "you" cannot be said to know anything because in that state "you" (that is, the bat in your place) would no longer be able to believe propositions and justify them, or experience anything in any sense that even remotely resembles the way humans do. So Nagel's problem involves a logical impossibility which renders it incoherent and therefore it cannot be used as a valid argument against physicalism or any other doctrine.

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Posted 08/01/09 - 04:26 PM:	#7
@Davidchalmers: "Now, of course identity theorists think that consciousness is physical. But they don't usually think that this identity is a priori -- they think it is something we discover empirically." Alternately identity theorists could take the model of scientific discovery based on refutation and conjecture. Identity would be an assertion whose implications were empirically testable. Thus identity theory would not be an (in some sense) probabilistic idea open to the chain of argument you outline here. Neither do I see conceivability having a reliable link to possibility. Some things which are conceivable are possible, and others are not. P-zombies are just as conceivable as 'colorless green dreams sleeping furiously'. I.e. syntactically expressible but semantically incoherent.
"Now, brothers, if I come to you and speak in tongues, what good will I be to you, unless I bring you some revelation or knowledge or prophecy or word of instruction?" - 1 Corinthians 14

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