Philosophy of Mind

Sellars on Mind and Language

Richard Brown Leave a comment

I found this very interesting lecture by Sellars where he talks about dot quotes and its relation to ontology and the mind-body problem…all good stuff and worth a listen. But what really caught my interest was his comments at the beginning of part F where he seems to admit that some kind of causal theory has to be right for the way thoughts work but not for the linguistic meaning…is there any other way to interpret these remarks? Also, does anyone else feel like they are listening to Jimmy Stewart talk about philosophy??

Update:

On my way home from class today I realized that what Sellars says in these lectures vindicates something I thought of after someone objected that on my view names would fail the Church translation test. t thought you could just dot quite your way out of it so it is nice to hear Sellars talking about dot quoting ‘Socrates’.

The Singularity, Again

Richard Brown 7 Comments

Yesterday I attended Dave Chalmers’ session of the Mind and Language Seminar where we discussed his new paper on the singularity. I have previously seen him give this talk at CUNY and I was looking forward to the commentary from Jesse and Ned and the discussion that followed.

Jesse talked for an hour summarizing the argument and making some objections. The two that stood out to me were his claim that Human extinction is more likely than the singularity (he outlined some cheery scenarios including alien attack, global pandemic, science experiment gone bad, as well as depressed teenager with a nanonuke). Jesse’s other objection was to Dave’s argument that a functional isomorph of a conscious entity would itself be a conscious entity. Dave uses his dancing qualia/fading qualia argument here. The basic idea is that if we were to actually undergo a gradual swapping of neurons for computer chips it seems counter intuitive to think that my consciousness will cease at some point, or that it will fade out. In the context of the singularity this comes up if we consider uploading our minds into a virtual environment; will the uploaded virtual entity be conscious? Dave thinks that the fading qualia/dancing qualia intuitions give us good reason to think that they will. The people who upload themselves to the virtual world will be saying things like ‘come on in; it’s fun in here! We’re all really conscious, we swear!’ so why wouldn’t we think that the uploaded entities are conscious? Jesse worried that this begs the question against the person, like him and Ned, who thinks that there is something about biology that is important for consciousness. So, yeah, the uploaded entity says that it is conscious, but of course it says that it’s conscious! We have stipulated that it is a functional isomorph! Jesse concluded that we could never know if the functional isomorph was conscious or not. Dave’s position seemed to be that when it comes to verbal reports, and the judgments they express, we should take them at face value –unless we have some specific reason to doubt them.

During discussion I asked if Dave thought this was the best that we could do. Suppose that we uploaded ourselves into the virtual world for a *free trial period* and then download ourselves back into our meat brain. Suppose that we had decided that while we were uploaded we would do some serious introspection and that after we had done this we sincerely reported remembering that we had had conscious experience while uploaded.  It seems to me that this would be strong evidence that we did have conscious experience while uploaded. Now, we can’t rule out the skeptical hypothesis that we are erroneously remembering qualia that we did not have. I suggested that this is no different than Dave’s view of our actual relationship to past qualia (as came out in our recent discussion of a similar issue). So, I cannot rule out that I did not have qualia five minutes ago with certainty but my memory is the best guide I have and the skeptical hypothesis is not enough to show that I do not know that I had qualia; so too in the uploaded case I should treat my memory as good evidence that I was conscious in the uploaded state. Jesse seemed to think that this still would not be enough evidence since the system had undergone such a drastic change. He compared his position to that of Dennett’s on dreams. According to Dennett, we think we have conscious experiences in our dreams based on our memories of those dreams but we are mistaken. We do not have conscious experiences in our dreams, just the beliefs about them upon waking. This amounts to a kind of disjunctivism.

I still wonder if we can’t do better. Suppose that while we are uploaded and while we are introspecting a conscious experience we ask ourselves if it is the same as before. That is, instead of relying on memory outside of the virtual world we rely on our memory inside the virtual environment. Of course the zombie that Jesse imagines we would be would say that has conscious experience and that it was introspecting, etc but if we were really conscious while uploaded we would know it.

Ned’s comments were short and focused on the possibility that Human intelligence might be a disparate “bag of tricks” that won’t explode. A lot of the discussion focused on issues related to this, but I think that Dave’s response is sufficient here so I won’t really rehash it…

I also became aware of this response to Dave from Massimo Pigliucci and I want to close with just a couple of points about it. In the first place Pigliucci demonstrates a very poor grasp of the argument that Dave presents. He says,

Chalmers’ (and other advocates of the possibility of a Singularity) argument starts off with the simple observation that machines have gained computing power at an extraordinary rate over the past several years, a trend that one can extrapolate to a near future explosion of intelligence. Too bad that, as any student of statistics 101 ought to know, extrapolation is a really bad way of making predictions, unless one can be reasonably assured of understanding the underlying causal phenomena (which we don’t, in the case of intelligence). (I asked a question along these lines to Chalmers in the Q&A and he denied having used the word extrapolation at all; I checked with several colleagues over wine and cheese, and they all confirmed that he did — several times.)

Now having been at the event under question I can’t rightly recall if Dave used the word ‘extrapolation’ or not but I can guarantee that his argument does not depend on it. Dave is very clear that it is not extrapolating from the “successes” of current AI that grounds his belief that we will develop Human level AI in the near-ish future. Rather his argument is that intelligence of the Human variety was developed via the process of evolution which is a ‘blind’ process that is dumb. It seems reasonable to assume that we could do at least as good a job as a blind dumb process, doesn’t it? If we can achieve this by an extendable method (for instance artificial guided evolution) then we would be able to extend this Human level AI to one that is superior to ours (the AI+) via a series of small increments. The AI+ would be better at designing AI and so we would expect them to be able to produce an AI++. This is a very different argument from the simple extrapolation from doubling of computing speed that Pigliucci lampoons. I don’t know which colleagues that Piggliucci consulted but had he asked me I could have set him straight.

Finally while it is certainly true that Dave is in no need of defending from me and I am the last person who has the moral high ground in matters of personal conduct but I have to say that Pigliucci shames himself with his adolescent ad hominem abuse; that is truly  behavior unbecoming to academic debate. So too it is bizarre to think that Dave is the reason philosophers have a bad rep when in fact it is behavior like Pigliucci’s that is more the culprit. Dave is among those who represent philosophy at its best; smart intellectually curious people thinking big and taking chances, exploring new territory and dealing with issues that have the potential to profoundly impact Human life as we know it…all with grace and humility. You may not agree with his conclusions, or his methods, but only a fool doubts the rigor that he brings to any subject he discusses.

Higher-Order Theories of Consciousness and the Phenomenology of Belief

Richard Brown Leave a comment

Next week I am heading up to SUNY Freedonia to give two talks as part of the Young Philosophers Lecture Series . Here is a rehearsal of the first talk which is my most recent attempt to show that Rosenthal’s HOT theory is committed to cognitive phenomenology

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The Identity Theory in 2-D

Richard Brown 17 Comments

I plan on writing a series of posts discussing various themes that came up in discussion at the online consciousness conference.

I have long been a type-type identity theorist. There was a time when I thought that I would write my dissertation defending a version of identity theory (in fact the very first talk I gave at a professional meeting was what I thought of as a ‘pre-prospectus’ available here: Saying “I Do” to Identity. I presented this as a poster at the ASSC in Antwerp and as a talk at the SPP in Barcelona (I called this my “European Identity Tour”))…When I approached Michael Devitt about the idea he said that people used to be interested in the identity theory but that people had moved on…it turns out that people are getting re-interested in the identity theory in the wake of work by people like Tom Polger, Chris Hill, and Ned Block. One thing that came out very clearly in the discussion is the difference between the identity theory that Block holds from the kind that I hold. The main difference concerns how we will eventually come to discover the mind-brain identities. Broadly speaking there are two different camps.

It is useful to remind ourselves of what the originators of the identity theory held. In “Is Consciousness a Brain Process?” U. T. Place says,

The answer seems to be that we treat the two sets of observations as observations of the same event in those cases where the technical scientific observations set in the context of the appropriate body of scientific theory provide an explanation of the observation of the man in the street. Thus we conclude that lightning is nothing more than a motion of electric charges, because we know that a motion of electric charges through the atmosphere, such as occurs when lightning is reported, gives rise to the visual stimulation which would lead an observer to report a flash of lightning (p. 58 in Chalmers 2002)

J.J.C. Smart in “sensations and Brain Processes” writes,

Why do I wish to resist [the suggestion that qualia are irreducibly psychial]? Mainly because fo Occam’s razor. It seems to me that science is increasingly giving us a viewpoint whereby organisms are able to be seen as psyico-chemical mecanisms: it seems that even the behavior of man himself will one day be explicable in mechanistic terms…That everything should be explicable in terms of physics (together of course with the descriptions of the ways in which the parts are put together –roughly, biology is to physics as radio-engineering is to electro-magnetism) except the occurrence of sensations seems to me to be frankly unbelievable. Such sensations would be “nomological danglers,” to use Feigl’s expression

We can see here an emphasis on the notions of explanation and parsimony. 16 years later David Lewis and David Armstrong establish the alternative camp. Lewis puts it most clearly when he writes,

Psychophysical identity theorists often say that the identifications they anticipate between mental and neural states are essentially like various uncontroversial theoretical identifications: the identification of water with H2O, of light with electromagnetic radiation, and so on. Such theoretical identifications are usually described as pieces of voluntary theorizing as follows. Theoretical advances make it possible to simplfy total science by positing brdge laws identifying some of the entities discussed in one theory with entities discussed in another theory. In the name of parsimony, we posit those bridge laws forthwith. Identifications are made, not found.

In ‘An Argument for teh Identity Theory,” I claimed that this was a bad picture of psychophysical identification, since a suitable physiological theory could imply psychophysical identites –not merely make it reasonable to posit them for the sake of parsimony. The implication was as follows:

Mental state M=the occupant of causal role R (definition of M)
Neural state N=the occupant of causal role R (by the physiological theory)
Therefore Mental state M=neural state N (by transitivity of =)

Nor is this peculiar to psychophysical identifications. He goes on,

…the usual account is, I claim, wrong; theoretical identifications in general are implied by the theories that make them possible –not posited independantly. This follows from a general hypothesis about the meaning of theoretical terms: that they are definable functionally, by reference to causal roles (Psychophysical and Theoretical Identifications)

In a recent paper on functional reduction Ned Block targets the Lewisian view in favor of the Place/Smart view. Here is what he says,

If we want to know why water = H2O, freezing = molecular lattice formation, heat = molecular kinetic energy, temperature = mean molecular kinetic energy, etc, we have to start with the fact that water, temperature, heat, freezing and other magnitudes form a family of causally inter-related “macro” properties. This macro family is mirrored by a family of “micro” properties: H2O, mean molecular kinetic energy, molecular kinetic energy and formation of a lattice of H2O molecules. (Of course a given level can be micro with respect to one level, macro with respect to another.) The key fact is that the causal and explanatory relations among the macro properties can be explained if we suppose that the following relations hold between the families: that water = H2O, temperature = mean molecular kinetic energy, heat = molecular kinetic energy and freezing = lattice formation. For example, why does decreasing the temperature of water cause it to freeze? Why does ice float on water? Here is a sketch of the explanation: The oxygen atom in the H2O molecule has two pairs of unmated electrons, which attract the hydrogen atoms on other H2O molecules. When the kinetic energy of the molecules decreases, (i.e. the temperature decreases) each oxygen atom tends to attract two hydrogen atoms on the ends of two other H2O molecules. When this process is complete, the result is a lattice in which each oxygen atom is attached to four hydrogen atoms.Ice is this lattice and freezing is the formation of such a lattice, which is why decreasing temperature causes water to freeze. Because of the geometry of the bonds, the lattice has an open, less dense structure than amorphously structured H2O (viz., liquid water)–which is why ice (frozen water) floats on liquid water.

Suppose we reject the assumption that temperature is identical to mean molecular kinetic energy in favor of the assumption that temperature is merely correlated with mean molecular kinetic energy? And suppose we reject the claim that freezing is lattice-formation in favor of a correlation thesis. And likewise for water/H2O. Then we would have an explanation for how something that is correlated with decreasing temperature causes something that is correlated with frozen water to float on something correlated with liquid water, which is not all that we want. The reason to think that the identities are true is that assuming them gives us explanations that we would not otherwise have and does not deprive us of explanations that we already have or raise explanatory puzzles that would not otherwise arise. The idea is not that our reason for thinking these identities are true is that it would be convenient if they were true. Rather, it is that assuming that they are true yields the most explanatory overall picture. In other words, the epistemology of theoretical identity is just a special case of inference to the best explanation. (See Block, 1978a; Block, 2002; Block & Stalnaker,1999).

Block goes on to argue that the Lewis style view is incompatible with the metaphysics of physicalism. Block distinguishes between ontology and metaphysics. Ontological physicalism is just the claim that in our ontological commitment to the existence of qualia we commit ourselves only to physical entities (ontological dualists deny this). Metaphysical physicalism is the claim that qualitative properties are essentially or metaphysically physical. That is to say that all qualitative properties will share the same physical properties in so far as they are physical. the Lewis style physicalism is ontologically but nit metaphysically physicalist. This is because as it happens all of the realizers of mental states are physical but metaphysically pain is a functional state for Lewis and only contingently a physical state. Metaphysical physicalism –real physicalism in Block’s view– says that it is not contingent but necessary that pain is a physical state.

But if we adopt the 2-D framework and put the Lewisian claims in terms of it this is no longer a problem. On this kind of view the functional definition gives us the primary intension of ‘pain’ and the physical state gives us the secondary intension. This allows us to treat ‘pain’ just as we do ‘water’. ‘Water is H2O’ has a contingent primary intension and a necessary secondary intension. So we can update Lewis view that ‘pain’ isn’t a rigid designator as the claim that the primary intension of pain is contingent (just like ‘water’). ‘Pain’ is still a rigid designator in the ordinary sense that its secondary intension is necessary. In all worlds considered as counter-factual pain is a brain state. However we accommodate the conceivability of Martians and disembodied minds by noting that in some worlds considered as actual pain is not a brain state (just as in some worlds considered as actual water is not H2O). This does not threaten the identity; it is the usual way that theoretical identities work. Notice also that this 2-D identity theory is a metaphysical physicalism in Block’s sense and not merely an ontological physicalism.

Of course the real resistance to the 2-D Lewisian identity theory is that qualitative states are not supposed to be functionally definable. In fact Block and Chalmers often talk as though qualitative properties are definable as ‘the not functionally definable properties of experience’ (more on that later). If that is your view then you cannot do the Lewsian deduction of the identity. What are we to make of this? I will come back to this in the next post.

The Singularity and Simulation

Richard Brown 1 Comment

(cross-posted at Brains)

There is a nice video of a recent talk by David Chalmers on the singularity available here. Dave also summarizes the argument in a recent post at his blog Fragments of Consciousness (here). He also gave this talk at the Graduate Center, which is where I saw it last Wednesday. It is an excellent talk and I hope it starts people talking about these interesting issues. Assuming you believe that AI is a possibility I find the general line he is pushing very persuasive and would be interested to hear what others thought about it.

One thought that I had was that if the second premise of the argument is right then we might have some kind of evidence that we are not living in a simulated world. If we were we would be the AI and the second premise says that once you have AI it will be a matter of years before you have AI+, but we haven’t had AI+ yet (i.e. strong A.I.) so we are not AI. When I asked about this Dave responded that ‘a matter of years’ should be interpreted as in the time scale of the next world up. If we are indeed in a simulated world then the simulators of our world could presumably manipulate the time scale in the simulated world. So what may seem like a long time to us could be a few seconds for them. Ah well, I guess we still can’t be sure that we aren’t in the Matrix.

This allows me to clarify the point of my previous post. In discussion with Dave about it he pointed out that what I describe is just one kind of dualism and that it is not the kind that the zombie argument deals with. This is a fair point. Looking back at the post I see that I was sloppy in presenting the argument. I should not have been saying that the zombie argument by itself is an argument that we are in a simulated world. What I should have said is that this account of what a nonphysical property is is the only one that is one the table. But when we adopt this as a theoretical account of what non-physical properties are even zombies can have them and so they do not seem to threaten physicalism. If there is some other account of what a nonphysical property is then we can examine it and one cannot say that an obvious example of a nonphysical property is seeing green or feeling pain. What is needed is an account of what it would mean to say that feeling pain is nonphysical. I, for one, can’t even conceive what that would mean except in the way Dave does in his matrix paper.

The Matrix & Nonphysical Properties

Richard Brown 3 Comments

(cross-posted at Brains)

I have long wondered what dualists mean when they speak of nonphysical properties. Today I was reading Chalmers’ paper The Matrix as Metaphysics and he says something that may shed some light on the way in which he thinks of nonphysical properties. He argues that the matrix scenario can be construed as a metaphysical hypothesis about the ultimate nature of the physical world. If this is right then there is a sense in which dualism is true. The mind is a distinct entity that exists outside of physical space-time and causal interacts with the physical body. This is because the physical theory that is true of reality in the matrix is a computational theory on which the ultimate things which exist are bits (zeros and ones). Thus brains in the matrix are ultimately composed of bits and when people in the matrix talk about brains they ultimately are talking about bits. The brain which is outside of the matrix is not composed of bits (let us assume). It is ultimately composed of something else (let’s say strings). Thus the brain outside the matrix, when viewed from the perspective of someone who is in the matrix, is nonphysical. It is not something that could be deduced from a completed matrix microphysics (which would be phrased in terms of ones and zeros).

One might wonder whether a completed matrix physics would have to be supplemented with (from the perspective of the matrix) nonphysical laws in order to capture outside the matrix facts or whether we might view the truly completed matrix physics as being expanded to include the outside the matrix physics. On this latter view the laws of matrix-physics would be a special subset of the laws of outside-physics. If this were true then the matrix-physics would not be complete until it was expanded to include outside-physics and physicalism could still be true. One might also wonder whether people in the matrix had largely true outside-physics beliefs since the matrix world is a deliberate simulation of outside-physics.

But even setting aside these issues there are strange results. Suppose that physicalism is true and that consciousness is a purely physical property of the brain. Let us also assume that this is true of a brain that is not in a matrix scenario. Call this scenario 1. Now imagine that a physical duplicate of this physicalist brain that has been in a matrix scenario since birth Call this scenario 2). Then physicalism is true in scenario 1 and dualism is true of scenario 2. But these brains are physically identical! Furthermore this shows that we could not resolve the dispute between the physicalist and the dualist until one was in a position to determine whether or not one is in a matrix scenario. Since Chalmers himself admits that he cannot a priori rule out that he is not in a matrix scenario he must also admit that he is not in a position to a priori tell if physicalism or dualism true. So, suppose that we are actually in a matrix scenario then conceiving of zombies is just conceiving of a computer simulation composed completely of NPCs (non-player characters). But this doesn’t show that physicalism is false, since physicalism is best construed as the claim that lines up with the first brain; since with this understanding of nonphysical physicalism turns out to be nothing but the hypothesis that we are not in the matrix.

But even if we were in the matrix there is a sense in which we can say that physicalism is still ultimately true since in the above envisioned world qualitative properties turn out to be identical to properties which are physical in terms of outside-physics (since these properties are the very same as the ones in the world where physicalism is true).

Zoombies are creatures that are nonphysically identical to me in every respect and which lack nonphysical qualitative properties. I have in the past suggested that one way to conceive of zoombies is as Cartesian minds that only have thoughts but no qualia but now we can put it in terms of matrix scenarios. A zoombie has all of the same nonphysical properties that I in fact do. Suppose that I am in fact in scenario 2 above. Then a creature that has all of the nonphysical properties that I in fact do will have a brain that is identical to my outside-brain. This is to imagine scenario 1.

The traditional zombie is a creature that is physically identical to me and lacks consciousness. Now suppose that I have a zombie twin who is in a matrix scenario since birth. My matrix zombie twin has nonphysical properties (which are the very same properties that I physically have) but no qualitative properties. So, whether one has nonphysical properties or not is simply a matter of whether one is in the matrix or not. Chalmers’ defense of nonphysicalism can thus be seen as a defense of the claim that we are in the matrix.

Zoombie Round-Up

Richard Brown 3 Comments

There has been a bit of discussion of zoombies in the blogosphere of late and I want to keep track of them all so that I can respond to them so I am posting links to them.

1.) Intentional Objects‘ David Gawthorne

Richard Brown’s Zoombies and Shombies

2.) Brain Scam‘s Tony Alterman:

Zombie, Scmombie –Richard Brown’s Efforts to Ressurect Materialism

(and his reply to my reply) Return of the Zombie

3.) And then there’s Richard Chappell’s responses.

In our latest exchange he has acknowledged that the primary and secondary intensions of statements in Q may diverge but seems to think that translating those statements into “semantically neutral” language will still let the argument go through. So, just was “the watery stuff isn’t H2O” comes out true at Twin Earth, “the painful stuff isn’t C-Fiber firing” comes out true at the zombie world. But this move won’t work. Here is what Chalmers has to say about this:

Given the discussion above, one might try generating an anti-materialist argument by simply substituting primary possibility for metaphysical possibility in the original argument.

(1) P&~Q is conceivable

(2) If P&~Q is conceivable, P&~Q is 1-possible

(3) If P&~Q is 1-possible, materialism is false.

_______________

(4) Materialism is false.

On this reading, (1) and (2) are both plausible theses, but (3) is not obviously plausible. The reason is that materialism requires not the 1-impossibility of P&~Q but the 2-impossibility of P&~Q. That is, materialism requires that it could not have been the case that P were true without Q being true. This is a subjunctive claim about ordinary metaphysical possibility, and so invokes 2-impossibility rather than 1-impossibility.

A materialist might reasonably question (3) by holding that even if there is a world W verifying P&~Q, W might be a world with quite different ingredients from our own. For example, it might be that W does not instantiate true microphysical properties (those instantiated in our world), such as mass and charge, but instead instantiates quite different properties: say, pseudo-mass and pseudo-charge, which stand to mass and charge roughly as XYZ stands to H2O. Likewise, it might be that W does not lack true phenomenal properties, but instead lacks quite different properties: say, pseudophenomenal properties. If so, then the possibility of W has no bearing on whether true microphysical properties necessitate true phenomenal properties. And it is the latter that is relevant for materialism.

Still, it may be that the gap between 1-possibility and 2-possibility could be closed. In particular, when a statement S has the same primary intension and secondary intension, then a world will verify S iff it satisfies S, so S will be 1-possible iff it is 2-possible. If P and Q both have primary intensions that coincide with their secondary intensions, then so will P&~Q, and we could run the following argument:

 

(1) P&~Q is conceivable

(2) If P&~Q is conceivable, P&~Q is 1-possible

(3) If P&~Q is 1-possible, P&~Q is 2-possible.

(4) If P&~Q is 2-possible, materialism is false.

_______________

(5) Materialism is false.

Here, the truth of (3) requires that both P and Q have primary and secondary intensions that coincide. (from The 2-D Argument Against Materialism)

Reflections on Zoombies and Shombies Or: After the Showdown at the APA

Richard Brown 1 Comment

The last three weeks have been extremely hectic for me. Starting with the Long Island Philosophical Society meeting (which was at LaGuardia and which I helped organize), and then the Pacific apa, and then when I got back the Felician Ethics conference (more about that later)…not to mention a pile of papers to grade and the search we are doing at LaGuardia…very busy indeed. Well things are starting to settle down a bit now and I wanted to reflect on what happened.

My talk went well. There was lively and helpful discussion. My commentator was Robert J. Howell from Southern Methodist University (coincidently the same commentator from Consciousness Online. A video of his comments is available there is anyone is interested). Robert brought up two interesting objections that I wanted to discuss.
The first was to the zoombie argument. A zoombie, you might recall, is a creature that is identical to me in every non-physical respect and which lacks non-physical qualitative consciousness. Robert argued that the zoombie argument was invalid since non-physical properties are necessary for qualitative consciousness (according to the dualist) but they need not be sufficient. That is, there might be a creature that was identical to me in all non-physical respects (that is, had all of the non-physical properties that I in fact do) but because it lacked a certain physical element these non-physical properties were ‘inert’ and so the creature did not have any conscious experience(a special kind of neuron, or a certain kind of firing by a neuron might be needed in order to ‘turn on’ the non-physical properties in such a way as to get consciousness experience of pain). If this is possible then the existence of zoombies does not show that dualism is false(what is nice about this is that this is exactly the same kind of move that a physicalist like me makes about the zombie world. What you are actually conceiving, and what is actually possible is a world that looks like ours but in not micro-physically identical to it. The exact parity between these two arguments is again striking).

I argued that for a creature to really be a non-physical duplicate it may be the case that it has to also be a physical duplicate. So if the dualist thinks that I need certain physical properties, or certain laws of physics, in order for me to consciously experience, say, pain, then that will be present in the zoombie world. So there cannot be inert non-physical properties in the zoombie world. If there were non-physical qualitative properties in the zoombie world they world they would result in conscious experience. This is not to deny that worlds like the one that Robert is suggesting are possible, they may be, but these worlds are not the zoombie worlds (compare: the physicalist like myself admits that there are physical worlds where there is no consciousness but these worlds are not physical duplicates of our world and so are not zombie worlds). The basic point is that the zoombie world is one exactly like our world; it has all of the same physical properties and all of the same laws and all of the same non-physical properties, but no non-physical qualitative properties. That world is conceivable and that world is the one that shows that property dualism is false.

Robert’s response was that if I allowed the dualist to claim that we needed to have complete micro-physical duplication in order to get non-physical consciousness experience (as opposed to merely ‘inert’ non-physical qualitative properties) then it looks like I am admitting that the traditional zombie world is conceivable since I hold that the zoombie world will now have to be a micro-physical duplicate of our world and also that the zoombie world lacks qualitative cosnciousness. But then zoombies are a kind of zombie! true zoombies are allowed to have non-physical properties (though not non-physical qualitative properties) so they may not be exactly like traditional zombies, but they are sufficiently alike to falsify my argument that zombies are inconceivable.
But I don’t need to claim that the zoombie world lacks qualitative consciousness entirely. All that I need is for the zoombie world to lack non-physical qualitative consciousness. So, since we are now allowing that zoombies must be complete physical duplicates of me then they must, according to me, have physicalist consciousness. So this move that Robert is suggesting just again points out the stalemate that is inevitably reached when one tries to resolve empirical issues with a priori methods. If physicalism is true then the modified zoombies will have consciousness of a physical kind, where as if dualism is true then, according to them, these modified zoombies will have non-physical consciousness. If we knew how the actual world was then we would be in a position to tell a priori (in Chalmers’ sense) which of these is correct. But now all we can tell a priori is that given one thing something else follows. This is exactly the position we are in with respect to things like Goldbach’s conjecture. If Goldbach’s conjecture is true then every even number greater than 2 can be expressed as the sum of two prime numbers if it is false then it is not the case that every even number greater than two can be expressed as the sum of two prime numbers. From our point of view now it seems conceivable that it could go either way. But given standard assumptions about mathematics it cannot really go either way. If it is true, then it is necessarily true. We cannot at present tell which it is. The same is true with respect to the dualism/physicalism debate. A priori methods are useless to us given the epistemic position we are in. I grant that as we approach the ideal limit of we things which are not a priori now will become so, but that does us no good right now. The only way we can advance debates about the nature of consciousness, from where we are now, is by a posteriori empirical investigation.

The second objection that Robert raised (and which I haven’t addressed in my response over at Consciousness Online) is aimed at the Shombie argument. Shombies are creatures that are physically identical to me and which have consciousness and lack all non-physical properties. Shombies have received more attention than zoombies (in fact at the apa Katilan Balog advanced an argument of this type. Robert’s objection to Shombies was that it amounted to no more than the following “it is conceivable that physicalism is true, physicalism is a modal thesis and if true at any world is true at all possible worlds, therefore since it is true at one possible world it is true of our world”. This way of putting it makes the shombie argument sound like a version of the ontological argument as advanced by people like Plantinga. But this kind of argument isn’t very interesting, Robert continued, because it is not as though we have found something from which the truth of physicalism follows. We have simply insisted that it is true.

Now in my response I complain that this is exactly what is going on in the traditional zombie argument, but later in conversation I tried to adapt the strategy that Chalmers uses in response to Yablo meta-modal argument against CP. Chalmers argued that what he was doing was merely conceiving of one particular possible world and not the entire space of possibilities. So too, I am merely conceiving of one possible world and not making meta-modal claims about the space of possibilities. true, physicalism is a modal thesis and so if it is true at one world it follows that it is true for all physically identical worlds, but I don’t need to conceive of the shombie world in that way. All that I need to do is to conceive of the shombie world as being physically identical to our world and as having a creatures there who have conscious experience in exactly the same way that I in fact do. This is not to conceive of physicalism being true and so not to employ the argumentative strategy that Robert criticizes. This is because the shombie argument is only designed to show that dualism is false, not that physicalism is true. For dualism to be true there must be a world that is physically identical to ours which lack qualitative consciousness. Shombies show that there is no such world since the world that is physically identical to ours is a world with conscious experience. So just the conceivability of one possible world is in question and that is enough to show that dualism is false.

Towards the end of the discussion David Pitt made a plea for agnosticism. Nobody knows what is going on here, so there is no more reason to prefer physicalism as there is to prefer dualism. This is an empirical matter and we are not in a position to really say which is true. But my argument was that there is no a priori reason to prefer one theory over the other. There are a posteriori reasons to prefer physicalism over dualism. A meta-induction over the history of science seems to me to clearly show that appeal to non-physical properties are superfluous. Every time we posit something like this it is explained away 1000 years later. We also, as Robert pointed out, have good a posteriori reason to accept causal closure of the physical and good reason to think that mental properties are causally efficacious, and therefore good a posteriori reason to think that mental properties are physical. So all in all physicalism seems to me to have the upper hand. But I agree with David that we are not in a position to say for sure what is going on with the mind. However, the failure of a priori arguments against it and the a posteriori arguments in favor of it make it reasonable to think that it is a live possibility. In fact, given the utter mysteriousness of non-physical properties there is strong presumptive evidence against dualism and for physicalism. This is what my view has in common with Perry’s antecedent physicalism. We should assume that physicalism is true unless we have good reason to think otherwise. We don’t, as of yet, have good reason to think otherwise and so we should assume that it is true.

Torin Alter made several good comments, but I can’t recall all of them. Since I had been claiming that whether physicalism was true was an a posteriori empirical matter he asked me if I thought there was some experiment that we could do which would show that dualism was true or that physicalism was false. I don’t think that there is. What I think is that as we approach the ideal limit if scientific investigation we will either start to see that we can make deductions from physical states to qualitative states in the way that the physicalist thinks or that we will not be able to do this. So it is not as though one experiemtn will vindicate physicalism or falsify dualism. Rather it is that at the limit the deduction will be possible or they won’t. This is what will determine which view is ultimately true of our world. Now, it may be the case that we don’t need to get to the limit, but only sufficiently close to it to see how the deduction could be made (like the position that we are in right now with respect to table facts. Maybe we can’t actually make the deductions because of restriction on our computing power and lack of complete knowledge of physics but even so we can see that it could be done). He also pointed out a useful terminological point. He pointed out that I sometimes talk as though prima facie conceivability is an epistemic notion whereas ideal conceivability is a metaphysical notion but according to Chalmers both of these notions are purely epistemic notions. I think that the confusion follows from my trying to go back and forth between Chalmers’ terminology and Kripke’s terminology. I take it that the distinction between epistemic possibility and metaphysical possibility from Kripke maps onto the prima facie/ideal conceivability talk from Chalmers. Epistemically possible means that for all I know it may be possible, but it may not be possible. Metaphysically possible means that it is a ‘real’ possibility in the sense that there is a possible world corresponding to it. So it is epistemically possible that Goldbach’s conjecture is true, and it is epistemically possible that it is not. But both cannot be metaphysically possible. Thos who want to preserve the link between conceivability and possibility will, like me, think that contradictory epistemic possibilities both seem conceivable but both are not metaphysically possible. I take it that prima facie conceivability means ‘seems conceivable but on ideal reflection might not be’, whereas ideal conceivability means ‘conceivable on ideal reflection’ (ignoring primary/secondary and positive/negative distinctions). Am I wrong about this?

Michael Tooley wanted to know how I was characterizing the physical/non-physical distinction. He wanted to maintain (so it seemed to me) that a property was non-physical if in order to fully know about it one has to experience it from the first person. This seems wrong to me. I use ‘physical’ in the way that Chalmers uses it (I hope) as ‘property which figures in a completed micro-physics or can be deduced from such properties’. The second clause in that description of physical leaves open the possibility that qualitative properties have to be ‘had’ in order to fully understand them. It may be the case that one does not truly have the concept of blue unless one has actually seen blue. But this doesn’t mean that we couldn’t make deductions from physical properties to qualitative ones. We may need to have the experience in order to acquire the concept but once we have the concept we can make the requisite deductions. This is exactly the strategy that Chalmers and Jackson argue for in defense of the claim that physicalism should entail qualitative properties. We may need to acquire a concept of water from experience in order to make deductions from physical facts to water facts, but the deductions still count a a priori because the concept just enables the deduction it doesn’t play any justificatory role in the deduction. The same is true in this case. So if it is true that we need experience in order to fully have the concepts in question there is no reason to think that we shouldn’t be able to make the deductions in question. This is partly why the Knowledge argument is question begging. If Mary knows all of the physical facts about color and what it is like for Mary to see red is a physical fact (or can be deduced from a physical account) then she should know it in her room. To assume otherwise is to beg the questions against phsyicalsim. Robert seemed to agree with this line of argument and suggested that he is working on something similar that he calls ‘subjective physicalism’.

Ok this is getting ridiculously long, so I will stop now.