David Chalmers' Fixation With Logical Possibility (2)

Contents:

5. Logical Possibility and Natural Possibility
6. Zombies
7. Saul Kripke
8. Chalmers & Goff: Conceivability to Possibility
9. Two More Conceivings

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conceive: to develop an idea; to form in the mind; to plan; to devise; to originate; to understand (someone).

conception: the act of conceiving.

The state of being conceived.

The power or faculty of apprehending of forming an idea in the mind; the power of recalling a past sensation or perception; the ability to form mental abstractions.

An image, idea, or notion formed in the mind; a concept, plan or design.

Logical Possibility and Natural Possibility

One may think that only natural (or empirical) possibility is of interest to most people – both laypersons and experts. Indeed David Chalmers himself (sort of) states that in the following:

“It is logically possible that a plate may fly upward when one lets go of it in a vacuum on a planetary surface, but it is nevertheless empirically impossible. The laws of nature forbid it.”

Yet logical (i.e., not natural) possibility still permeates Chalmers' entire work. And, as we shall see, so too does conceivability; which he strongly ties to logical possibility.

Thus, with a concrete (as it were) example, Chalmers says:

“The key question in this chapter is whether absent or inverted qualia are naturally or empirically possible.”

Indeed Chalmers goes further when he says that

“establishing the logical possibility of absent qualia and inverted qualia falls far short of establishing their empirical possibility”.

He opposes this to logical possibility. However, as just stated, logical possibility also looms large in Chalmers' work. Indeed his references to natural possibility hardly make sense when taken out of the context of logical possibility. Thus both logical and natural possibility gain much of their purchase by being opposed to one another.

Chalmers himself sums up one major problem with logical possibility (this was touched upon in Part One) when he says that

“[t]here are a vast number of logically possible situations that are not naturally possible”.

That means that there must be mightily good philosophical (or scientific) reasons to spend time on a given logical possibility. (It's easy to believe that there are good reasons when, for example, consciousness is being discussed.) That is, surely it must pay philosophical dividends to do so. Having said that, there's a very large number of uninstantiated natural possibilities too. Chalmers himself gives us an example when he tells us that

“[i]t is even naturally possible (although wildly improbable) that a monkey could type Hamlet”.

So what, philosophically, can we draw out of that natural (“although wildly improbable”) possibility? Well, we can draw one thing out: that it's naturally possible. And that's enough for some philosophers. But what else? Well, at a superficial level, it shows us that all sorts of bizarre things are naturally possible. So if it's naturally possible that a monkey could type Hamlet, then it's also naturally possible that an ant could take over the world. Why? Because all it takes for something to be naturally possible is that it “conforms to the laws of our world”. So, as far as I can see, a Nietzschean super-ant does appear to conform to the laws of of our world. That is, this ant and its actions don't “violate[] the laws of nature of our world”.

So thank God there are limitations to logical possibility, at least according to Chalmers himself. For example, Chalmers writes:

“God could not have created a world with male vixens, but he could have created a world with flying telephones.”

Is the above much of a limitation? Not really. That's because male vixens are conceptually impossible. In that basic sense, then, we aren't being told anything about the world – we're being told about (as it were) conceptual exclusion or conceptual necessity. So, in that basic sense, flying telephones are far more interesting than male vixens.

Zombies

Chalmers believes that zombies are worth discussing because “there seems to be no a priori contradiction in the idea” of zombies. There's also no a priori contradiction in a human being having 106 legs; though such a thing won't tell us much. So it's not just the bare possibility that zombies exist. It's that the possibility can tell us something about the world.

Thus we can conceive of a physical system that's note-for-note identical to us but which doesn't have consciousness. Such as system would therefore be a zombie. 

Alternatively, it may be a "zombie-invert" in that some of its experiences are inversions of those of human beings. The invert-zombie has the same nuts and bolts as us; though nevertheless it has different experiences. So the inverted zombie is still allowed his/its experiences.

There's also the “partial zombie” who also has experiences; though not as many as those of human beings. (Perhaps he/it can only feel pain.)

The point is that all these zombies are physically identical to us from the third-person point of view - and their behaviour will also be indistinguishable from us.

So what about their first-person point of view? “What is it like” to be a zombie of whatever kind? Well, there's nothing it's like to be a zombie! (Except in the partial and inverted zombie cases.)

On a larger scale. What about a physically identical universe which doesn't give rise to consciousness; though which does give rise to zombies? Can we say that such zombies are indeed "naturally possible"? However, according to our own laws of nature, they probably couldn't exist. That is, given identical physical and bodily facts, then such a universe couldn't help but give rise to consciousness.

Let’s take this further.

There could be an identical universe that didn't give birth to consciousness. If this were the case, then Chalmers concludes that consciousness must be something above and beyond the physical if such a counterfactual scenario is possible.

Chalmers himself argues that

if we can conceive of zombies in our world (or at other worlds),

then zombies are "metaphysically possible".

Chalmers supports his conceivability arguments by arguing thus:

“If P & -Q is conceivable, [then] P & -Q is metaphysically possible [as well as being] supported by general reasoning.”

Is there such a link between conceivability and possibility? If so, what kind of link is it? In other words, just as there are arguments about certain claims being conceivable and therefore possible, is that link itself grounded in conceivability or possibility (or both)? What is the nature of the link between conceivability and possibility?

Chalmers codifies all this with a logical argument:

i) It is conceivable that P & not-Q.

ii) If it is conceivable that P & not-Q, then it is metaphysically possible that P and not-Q.

iii) If it is metaphysically possible that P & not-Q, then materialism is false.

iv) So materialism is false.

We can see Chalmers’ slide here from conceivability to metaphysical possibility. The position above can be summed up this way.

i) Can we conceive a round square? No.

ib) Then a round square isn't metaphysically possible.

ii) Can we conceive of a man with five legs? Yes.

iib) Then a man with five legs is metaphysically possible.

Again, what are we supposed to gain or achieve by saying that mile-high unicycles are conceivable and therefore possible? Where does it take us? Here:

Zombies are logically possible because they are conceivable.

Or contrawise:

If zombies are conceivable, then they are logically possible.

Saul Kripke

Kripke said that he was working with his own “Cartesian intuitions” when he tackled the mind-body problem. And many of those intuitions were about what is and what isn't logically possible. It's also fairly clear that Chalmers has Kripkean intuitions on the same subject.

Kripke is an interesting philosopher to bring into this debate because, prima facie, he seems to hold two mutually-contradictory positions on conceivability (or on the philosophical use of the imagination).

In the first instance, Kripke tell us about an act of imagination which misleads us (metaphysically speaking). He writes:

“... we thought erroneously that we could imagine a situation in which heat was not the motion of molecules. Because although we can say that we pick out heat contingently by the contingent property that it affects us in such and such way...”

Thus the conceiver has conceived of the effects of the motion of molecules on bodies and the environment; though he hasn't conceived of heat actually being something other than the motion of molecules.

Let's say that heat is XYZ (i.e., something which isn't to do with molecular motion). What is it to conceive that heat is XYZ (i.e., something static) rather than molecular motion?

Imagination (or what we can conceive), on the other hand, can also tell us something important (as well as true) about the world. In Kripke's words:

“[J]ust as it seems that the brain state could have existed without any pain, so it seems that the pain could have existed without the corresponding brain state.”

Kripke stresses our ability to imagine a pain state without its correlated brain state (formerly characterised as the “firing of C-fibres”). Thus Kripke concludes:

If we can imagine mental states without their correlated brain states, then such states are possible.

Or, alternatively, Kripke is saying that there's no necessary identity between mental states and brain states.

Kripke, on the other hand, again claims that those who imagine heat being caused by something that's not “molecular motion” aren't really imagining heat at all. They just think that they are because they've based their act of imagination on the contingent properties of heat – its affects on persons and the environment.

Chalmers & Goff: Conceivability to Possibility

Asadullah Ali Al-Andalusi makes a distinction between the words 'conceive' and 'imagine'. He states:

“Let's not reduce my argument to only one of the terms I used: 'imagination'. I also used the word 'conceive'.”

The words 'conceive' and 'imagine' are not synonyms. However, everything that's can be said about imagination (at least in Andalusi's case) can also be applied to the word 'conceive'. Exactly the same problems arise.

Despite that, Al-Andalusi explains a distinction which can be made between conceiving and imagining. He continues:

“Imagination is the the result of experiences and the minds ability to mold them into different forms or to conclude connections between them. It takes two to tango in this regard. Conception is more abstract and doesn't require external experiences at all.”

Nonetheless, imagination may still be required to juxtapose (or 'tango' with) one's 'conceptions'. Even if conceptions (does Andalusi mean concepts?) are abstract entities, it will still require the imagination to juxtapose or use them.

In any case, there are naturalist (as well as plain old empiricist) explanations as to why the mind is “capable of conceiving of possibilities that the external world does not offer through direct experience”. The thing is that the mind doesn't really move beyond experience in these instances (though it may in others). It simply plays with experiences and juxtaposes them to create something that doesn't itself exist in experience.

Chalmers himself says that

“a claim is conceivable when it is not ruled out a priori”.

Put simply, there'll be an indefinite (infinite?) number of scenarios (or claims) which can't be “ruled out a priori”. Even the existence of shark with legs or mushrooms with a sense of humour can't be ruled out a priori. In other words, the only things which can be ruled out a priori are claims/scenarios which break known logical laws or which contain contradictions. Thus the conceivable universe (as it were) could be highly populated with strange and bizarre entities, conditions, events, etc.

Chalmers offers his own example of these conceivable. He says that it's “conceivable that there are mile-high unicycles”.

Philip Goff (when discussing Chalmers' position) expresses his view about the importance of conceivability in this way:

“If P is conceivably true, then P is possibly true.”

This can also be expressed in possible-worlds terms thus:

“If P is conceivably true (upon ideal reflection), then there is a possible world W, such that P is true at W considered as actual.”

Or, less technically, Goff says that

“Chalmers holds that every conceivably true proposition corresponds in this way to some genuine possibility”.

Yet all the above seems to assume that there's a determinate and precise meaning of the words “conceivably" and "conceivably true”. There's also a problem with the phrase “upon ideal reflection”. Goff must be aware of all this because he also says that

“conceivability entails possibility when you completely understand what you’re conceiving of”.

Goff puts the case for conceivability-leading-to-possibility more explicitly (i.e., less technically) when he states the following:

“We could not coherently conceive of the seven bricks being piled on top of one another in the way that they are in the absence of the tower. In contrast, it is eminently possible to conceive of our seven subjects of experience experiencing the colours of the spectrum, existing in the absence of a subject of experience having an experience of white.

This may very well mean that the conceivability-to-possibility argument may not get off the ground (at least in some cases) because nothing is really conceived of in the first place – even in the case of “ideal reflection”.

Goff goes much further than this logical principle. Not only is the argument that the conceiving of P is a reason for believing that P is metaphysically possible, Goff also argues that it may be the case that “metaphysical possibility is just a special kind of conceivability”. Note the use of the “is of identity” here. We're told that metaphysical possibility is conceivability. Thus it's not just that our conceiving of P may - or does - give us one reason to believe that P is possible. The very conceiving of P seems to bring about the metaphysical possibility of P.

Despite all the above, Goff himself expresses the position that conceivability may not always give us metaphysical possibility. That is, even if we do allow various moves from conceivability to metaphysical possibility, sometimes what we think is metaphysically possible still remains unbelievable. Or as Goff himself puts it:

“When metaphysical possibility is so radically divorced from conceptual coherence.... I start to lose my grip on what metaphysical possibility is supposed to be.”

It also seems that metaphysical possibility has moved beyond conceivability here – or at least beyond “conceptual coherence”. Thus that may mean that the move from conceivability to metaphysical possibility is sometimes illegitimate in the first place (Chalmers talks of ”misdescriptions"). That is, a specific conceiving may not warrant the metaphysical possibility which is derived from it. To stress that point, Goff also says that

“a radical separation between what is conceivable and what is possible has the potential to make our knowledge of possibility problematic”.

However, doesn't Chalmers himself provide a very tight link between conceivability and metaphysical possibility? If that's the case, then how can there ever be a “radical separation” between the two? (As Descartes argued about "human reason" which is properly used.) Thus if that link were to be broken, would that be due to the fact that some conceivings aren't really genuine conceivings at all? Either that, or some links between conceivings and possibilities simply aren't tight enough. Alternatively, perhaps some moves from conceivings to possibilities (as already stated) are completely bogus from the very beginning.

Two More Conceivings

“Water is XYZ”

Chalmers offers us another example in which we conceive of water being XYZ.

What does it mean to “conceive” the statement “Water is XYZ”? Surely it's no use Chalmers going into to detail if this isn't established in the first place.

Is the statement “XYZ is water” conceivable simply because we're simply imagining “watery stuff” (i.e., Chalmers' “primary intension”)? But are we conceiving of water actually being XYZ (i.e., rather than simply conceiving of water stuff)? Isn't that something completely different? So here goes:

i) The first act of conceiving has to take on board what XYZ actually is. (Say, if it's meant to be some kind of fictional - though possible – molecule.)

ii) And then one needs to conceive of this XYZ molecule (or otherwise) actually being water.

But what, exactly is being conceived here?

Here, as elsewhere, Chalmers doesn't make a distinction between imagining x (or P) and conceiving x (or P) - even though other philosophers have made such a distinction (as seen above). To put it basically, some philosophers argue that conceivings don't depend on the formation of any mental images. Therefore conceivings can be seen as being a more sophisticated form of (as it were).... imagining. That is, of imagination without imagery (if that isn't an oxymoron).

A Million-sided Object

Let's go into more detail about the nature of conceiving with Goff's own example of a million-sided object.

In one sense it can be said that we can indeed conceive of such a thing. Or, more helpfully, if I ask the conceiver this question:

What do you conceive of when you conceive of a million-side object?

Then the conceiver can reply by saying:

I conceive of an object which has a million sides.

But what does that mean? What, exactly, is he conceiving of? Is he simply saying the following? -

i) A million-sided object has a million sides.

ii) Therefore I have just conceived of a million-sided object.

Doesn't he simply (analytically) know that if something has a million sides, then he's conceived of an object having a million sides? Though is that really a case of his conceiving of a million-sided object or is it a statement of some kind of tautology?

For a start, no one can picture (or imagine) a million-sided object. So what's left? Goff says that “the concept million-sided object is transparent”. That is,

“it is a priori (for someone possessing the concept, and in virtue of possessing the concept) what it is for something to have a million sides”.

Goff's quote above is simply a rerun of what's already been said. That is:

(Q) What is it to conceive of something which has a million sides?

(A) It is to conceive of a million-sided object.

Here again, one simply restates the description of a fictional/possible object.

Perhaps my position is still too dependent on our contingent mental states and their content (e.g., mental images); whereas Goff's position may be strictly logical. Alternatively, perhaps Goff's position is strictly mathematical/geometrical (therefore abstract) in nature.

Thus perhaps it's an entirely logical and/or metaphysical point to state the following:

The concept [million-sided object] is conceivable and transparent.

But what does that claim amount to? Indeed how different is conceiving of a million-sided object to conceiving of a round square?

Nonetheless, it's certainly the case that a round square isn't in the same logical space as a million-sided object.

What would be easier to say is that a million-sided object could – or even does - exist - if only as an abstract object; though it still can't be conceived of. It this case we can cite René Descartes' example of a chiliagon. (I suspect that Goff had this in mind when he cited his own example.) This is a thousand-sided polygon.

The chiliagon is classed as a “well-defined concept” which, nonetheless, can't be imagined or visualised. Indeed, even if massive in size, it would still be visually indistinguishable from a circle. Thus it may even be the case that a chiliagon can't be conceived of either - even if we have a concept of it. Though that, again, depends on what's meant by the words “conceived of”. In any case, I would call a thousand-sided polygon a mathematical/geometrical abstract object; not a concrete object. In other words, it can't be found or even made. Nonetheless, that doesn't stop it from being a well-defined concept.

And even if the words “having a well-defined concept” and “conceiving of” are seen as virtual synonyms, it's still the case that both the layperson and the expert would need to conceive of (or have a well-defined concept of) what it is to be conceived of.

However, and as already stated, Goff believes that “the concept million-sided object is transparent”. Moreover,

“when one conceives of a million-sided object one completely understands, or is in principle able to reason one’s way to a complete understanding of, the situation being conceived of”.

Goff goes further when he says that

“it is a priori for the conceiver what it is for the state of affairs they are conceiving of [i.e., a million-sided object] to obtain”.

Thus we reach the important conclusion which Goff has been leading up to all along. Namely,

“that we can move from the conceivability (upon ideal reflection) of the states of affairs so conceived, to its genuine possibility”.

Despite all that, isn't the following definition and critical account (i.e., rather than a mere concept) of a chiliagon what must be conceived of? -

The quote above says that the “regular chiliagon is not a constructible polygon”. Nonetheless, is it still conceivable?

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David Chalmers' Fixation With Logical Possibility (1)

i) Introduction

ii) Six Logical Possibilities Before Breakfast

iii) René Descartes

iv) Logical Possibilities as Tools

There isn’t much technical argumentation in the first part of this piece about David Chalmers’ “arguments from logical possibility”. I suspect that many of Chalmers’ logical possibilities are indeed logical possibilities. I also suspect that many of his arguments are airtight. Thus, bearing that in mind, it’s not surprising that the philosopher David Lewis wrote the following about Chalmers’ book The Conscious Mind:

“Legions of materialists are no doubt busy writing their rejoinders; but there will be few points left for them to make that Chalmers hasn’t made already. We of the materialist opposition cannot go on about how he has overlooked this and misunderstood that — because he hasn’t.”

Nonetheless, its worth stating here that this piece has virtually nothing to do with my own position on materialism. Instead, it’s about the philosophical status of logical possibilities — which an “anti-materialist” could (at least in theory) agree with.

I’ve just mentioned Chalmers’ book The Conscious Mind. Chalmers introduces a logical possibility on almost every page of that book. In it he talks about “an angel world”, “flying telephones”, “ectoplasm” and a monkey who writes Hamlet. Admittedly, most of these logical possibilities are of little interest to Chalmers. That’s either because they’re hugely improbable or because they don’t help him philosophically. It’s primarily (philosophical) zombies which he specialises in — and it is these logically-possible creatures which help him philosophically. Indeed isn’t the position of panpsychism (which Chalmers also — at least in part — endorses) itself very reliant on logical possibility? (For example, it’s logically possible that an electron or stone has “phenomenal properties”.)

Not only is Chalmers’ keenness on logical possibilities a philosophical position, logical possibilities also help him advance one of his positions within philosophy. To quote Chalmers himself:

“I am not the first to use the argument from logical possibility against materialism. Indeed, I think that in one form or another it is the fundamental anti-materialist argument in the philosophy of mind.”

Chalmers and other “anti-materialists” require logical possibilities in order to advance anti-materialism. In other words, their arguments only work if one countenances all sorts of strange logical possibilities. This isn’t to say that materialists (as well as other kinds of philosopher) don’t themselves rely on logical possibilities in various ways — though they don’t do so nearly so often as philosophers like Chalmers.

Chalmers is explicit about his philosophical use of logical possibilities when he says that

“the question is not whether it is plausible that zombies could exist in our world, or even whether the idea of a zombie is a natural one; the question is whether the notion of a zombie is conceptually coherent”.

Thus if state of affairs A (or proposition P) is “conceptually coherent”, then A (or P) is also logically possible. All this is tied together by these three statements:

1) That which is conceivable is therefore also logically possible. 
2) State of affairs A (or proposition P) is conceivable because conceptually coherent. 
3) And state of affairs A (or proposition P) is conceptually coherent because it is conceivable. 

So when a philosopher cites various logical possibilities, all sorts of philosophical positions become available… or possible. That’s primarily because once a given philosopher sets a particular logical possibility among the pigeons, then it’s surely the duty of other philosophers to tackle that logical possibility. And if they don’t, then surely they’re philosophical philistines… or “verificationists”. Indeed Chalmers lays his cards on the table when he states this:

“In general, a certain burden of proof lies on those who claim that a given description is logically impossible.”

This means that there’s a lot of weight attached to logical possibilities. The importance of logical possibilities is made clear when Chalmers cites one specific example:

“So even if a zombie world is conceivable only in the sense in which it conceivable that water is not H2O, that is enough to establish that consciousness cannot be reductively explained.”

In other words, logical possibilities (as well as — as it were — conceivables) serve a larger philosophical purpose.

My points above may seem too strong. Nonetheless, Chalmers did say that

“the argument from logical possibility [is] the fundamental anti-materialist argument in the philosophy of mind”.

In other words, citing logical possibilities isn’t just another tool — it is the tool to fight materialism (perhaps much more too). Yet Chalmers suggests that we shouldn’t get “too worried about odd things that happen in logically possible worlds”. However, he then immediately takes that back by saying that “there is room to be perturbed by what is going on”.

Six Logical Possibilities Before Each Breakfast

David Chalmers says that there are innumerable logical possibilities. And partly because of that, Bertrand Russell once wrote the following:

“No logical absurdity results from the hypothesis that the world consists of nothing but myself… and that everything else is mere fancy.”

Yet, despite writing the above, Russell went on to say that

“[b]ut although this is not logically impossible, there is no reason whatever to suppose that it is true; and it is, in fact, a less simple hypothesis, viewed as a means of accounting for the facts of our own life, than the commonsense hypothesis that there really are objects independent of us, whose action on us causes our sensations”.

So we need to be given philosophical reasons as to why we should consider these (or other) logical possibilities — otherwise philosophers may end up spending their entire lives considering every logical possibility they can’t (as the philosopher David Lewis put it) “properly ignore”.

So if I carry on with Russell’s theme: 

1) When I wake up tomorrow morning, it’s logically possible that I will still be asleep. 
2) If I do genuinely wake up tomorrow morning (how could I know?), then it will be logically possible that the world’s entire population will be dead. 
3) And when I then move over to the tap, it will be logically possible that poison — not water — could come out of it. 
4) If it were to be genuine water, then it will also be logically possible that I could choke on that water. 
5) If I then look out of the window, it will logically possible that the town I see is a simulation of what I saw the day before... And so on and so on and so on.

In other words, I could think of six logical possibilities before each breakfast.

As with Russell, should I say that “although [they are] not logically impossible, there is no reason whatever to suppose that [they are] true”?

Russell’s next point is that the logically-possible hypothesis is (often?) “less simple” than the everyday (or common sense) one. He told us that 

“it is, in fact, a less simple hypothesis, viewed as a means of accounting for the facts of our own life”. 

In my examples, this means that: 

1) It is a less simple hypothesis to believe that I’m currently dreaming. 
2) It is a less simple hypothesis to believe that the entire world population is now dead. 
3) It is a less simple hypothesis to believe that poison (rather than water) will come out of my tap. 
4) It is a less simple hypothesis to believe that the water I drink will choke me.
5) It is a less simple hypothesis to believe that my window-view is a mere simulation of the facts.

Indeed isn’t it also less simple to believe in Chalmers’ zombies? 

However, Chalmers doesn’t care about that because the logically possibility of zombies is a means to a philosophical end.

Despite that, Chalmers appears to question his own use of logical possibilities when he uses the word “plausible”. That is, an indefinite numbers of things are logically possible — but how plausible (as well as probable) are they? Thus all Chalmers’ own logical possibilities are “logically compatible with the data”. However, “this is not enough to make them plausible”. To be more precise, this talk of plausibility is set within the well-known context that

“[f]or any scientific theory one can easily construct as ad hoc hypothesis that is empirically equivalent”.

In other words, as with scientific theories, many of Chalmers’ logical possibilities are of the kind that there can be no empirical way of establishing either their truth or falsity. They’re literally beyond the empirical or observational. That’s primarily because possibilities aren’t even meant to be either true or false. Possibilities are simply meant to be… possible. Then again, logical possibilities could become true or false — it’s just that they aren’t true or false.

René Descartes

Much of this talk about logical possibilities goes back to Descartes and his own arguments from logical possibility; which have inspired Chalmers (even if he updates them) and many other contemporary philosophers. Chalmers writes:

“[S]ome will find the argument for dualism that I have given reminiscent of the argument given by Descartes. Descartes argued that he could imagine his mind existing separately from his body, so his mind could not be identical to his body.”

As with my questions about Chalmers’ conceivings (or conceivables): what, exactly, did Descartes imagine? Of course the question of the status of imaginability in philosophical reasoning is often asked. What isn’t often asked is what, exactly, is being imagined in the first place.

This may remind readers of Bishop Berkeley’s argument that those who imagine an event which occurs without observers are actually imagining what it would be like from the observer’s perspective (e.g. when a tree is falling down). That is, we imagine some kind of disembodied mind (if with sensory receptors) observing the event. (Of course the idea of a disembodied mind observing a tree falling down is ironic when set within the context of this discussion about Descartes’ focus on imaginability and his belief in mind-body dualism.)

So did Descartes really imagine a disembodied mind? If he did, then what form did it take? Can a disembodied mind experience anything or does it simply indulge in pure thought? What kind of pure thought would that be? (Descartes did exclude sensations and the senses from the mind — see here.)

In any case, Chalmers then goes on to say that

“[t]his sort of argument [i.e., Descartes’] is generally regarded to be flawed: just because one can imagine that A and B are not identical, it does not follow that A and B are not identical (think of the Morning Star and the Evening Star, for example)”.

Again it can be asked whether or not Descartes did imagine a disembodied mind. If he didn’t, then this question of identity between A and B doesn’t even arise. Chalmers then makes the obvious point:

“Might not my argument make a similar mistake? The zombie world only shows that it is conceivable that one might have a physical state without consciousness; it does not show that a physical state and consciousness are not identical.”

So Chalmers offers his own Cartesian variant.

As it is, I simply can’t make sense of Chalmers’ riposte to (as it were) naïve Cartesianism. He writes:

“The form of the argument is not, ‘Once can imagine physical P.’ The form of the argument is rather, ‘One can imagine all the physical facts holding without the facts about consciousness holding, so the physical facts do not exhaust all the facts.’…”

To state the obvious, Chalmers is still relying on imagination here. In other words, is there really a big difference between

“One can imagine a physical P”

and

“One can imagine all the physical facts holding without the facts about consciousness holding.”

It’s still imagination which holds the trump card in both cases. And it’s this reliance on imagination that’s being questioned in both cases. At first glance, the words “[o]ne can imagine all the physical facts holding without the facts about consciousness holding” hold no water. In fact I’ve a problem knowing what it even means. 

For example, if we invert the argument, what would we imagine if we imagined “all the physical facts holding” and consciousness holding too? How do you imagine the consciousness of another being or entity? Through its linguistic and physical behaviour? Well, Chalmers himself wouldn’t accept that because it would be what some people call “reductionist”. So, again, what would we be imagining?

This is also like the point made about monism and pluralism by A.J. Ayer. He said that if monism were true, then the world would be exactly the same as that experienced by a pluralist. Similarly, how would

imagining all the physical facts holding without consciousness

differ from

imagining all the physical facts holding with the addition of consciousness?

Logical Possibilities as Tools

Despite all the above, it’s almost as if (at least at times) Chalmers wants to get logical possibility out of the way in order to deal with what he calls “empirical possibility”. Indeed he is explicit about this when he writes the following:

“It is useful to think of a logically possible world as a world that it would have been in God’s power (hypothetically!) to create, had he so chosen.”

In that sense, logical possibilities play the role that possible worlds do for those who don’t believe in their actual existence as “concrete” entities. (As David Lewis did when he used phrases like “worlds like our own”.)

The question is, then, what purpose do these logical possibilities and possible worlds play if they aren’t actually “actual”, “concrete” or instantiated? In the possible worlds case, much has been written about their efficacy for creating a semantics of modal terms, statements and whatnot. So one would assume that something similar follows for Chalmers’ own logical possibilities (such as zombies, “dancing qualia”, etc.). So it’s useful that Chalmers himself discussed his position on possible worlds. This means that what he says may provide us with a way in for discussing his position on logical possibility. Chalmers writes:

“I will not engage the vexed question of the ontological status of these worlds, but simply take them for granted as a tool…”

So I can rewrite that passage in the following manner:

I will not engage the vexed question of the ontological status of these logical possibilities, but simply take them for granted as a tool.

David Lewis (as hinted at a moment ago) asked cogent questions about all our talk of possibilities… and necessities. That is, rather than stress the fact that we can conceive of possibilities, Lewis was concerned with what logical and ontological status these possibilities have. Like “Plato’s Beard”, the very fact that we can conceive of them must surely mean that they have some kind of ontological status. According to Ted Sider’s David Lewis,

“we do have a reason to believe in his possible worlds: only by believing in them can we demystify necessity and possibility”.

Sider also offers us a pragmatic take on possible worlds which can also be applied to logical possibilities. He tells us that “it is sometimes reasonable to postulate things for theoretical reasons”. For example, “no one has ever directly perceived an electron”; though physicists “postulate electrons to explain the results of the experiments they perform”.

Sider then goes on to say that certain philosophers believe that possibilities (such as unicorns or Tom Hanks being a serial killer) have some kind of being even though they aren’t actual. Are these possibilities what Sider calls “ghostly things”? Not really. That’s because ghosts are believed to exist by some people. They simply have the ghostly property of, say, intangibility. (In other words, ghosts aren’t meant to be abstract entities.) Or as Sider puts it:

“Rather than making it the case that unicorns are possible, the existence of a ghostly unicorn would just mean that ghostly things are actual.”

So how should we see Chalmers’ logical possibilities within the context just discussed? In Sider’s words, “if possibilities are not ghostly entities, then what are they?”. If possibilities, such as Tom Hanks being a serial killer, are not ghostlike or anything else, then what are we talking about when we talk about them? What is Tom Hanks the serial killer, Pegasus or even the round square? 

Indeed what philosophical and actual status do Chalmers’ zombies have?

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To follow: 'David Chalmers' Fixation With Logical Possibility (2)'

Contents:

5. Logical Possibility and Natural Possibility
6. Zombies
7. Saul Kripke
8. Chalmers & Goff: Conceivability to Possibility
9. Two More Conceivings