Building Better Zombies

I’m warning you…

David Chalmers relies in no small way upon his so-called ‘philosophical zombies’ – entities that are like human beings in every respect, physical and psychological, the only teeny, tiny difference being that they are lacking conscious experience – to make his point about consciousness being a basic property, i.e. that it is a mental-kind term that may neither be functionalized nor emergent from some set of physical states of affairs. However, his example doesn’t (and shouldn’t) convince anyone who is not already friendly towards the sorts of consciousness-views offered by the various dualisms and panpsychisms floating about. To pick but one example, Daniel Dennett doesn’t think that Chalmers’ thought experiment does the trick (and is, in any case, very hostile to the proposition that there may be any mental properties which are not emergent from/reducible to physical facts/happenings [1]). And for what it is worth, I don’t think Chalmers’ thought experiment is very compelling either, even though I am more open than is Dennett to possibilities beyond run-of-the-mill reductive/eliminativist physicalist doctrines.

Why should I say this? Chalmers’ uses his zombies thus:

  1. It is conceivable that there might be some possible world wherein there
    are creatures with brains and psychologies such as our own, which are
    functionally identical to our own, but which are lacking conscious experience.
  2. Since it is conceivable that such beings could exist, consciousness is not an emergent property of physical systems assembled (physically or functionally) like our brains, otherwise the zombies in question would be conscious as well.
  3. As such, we may conclude that consciousness is neither simply a product of physical systems arranged in the right way nor functional systems of the right sort. [2]

Obviously, this is a very simplified presentation of his argument (or at least, of the version of his argument with which I am familiar), but it captures something of its thrust. As should be apparent, it is the second premise that causes the argument to fail – simply because something implies no logical contradiction, it does not follow that it is actually possible (in this world or any other). It may well be that in actuality any number of functionally appropriate systems (of which human brains are but one example) will be conscious and nothing else besides – which, not incidentally, is precisely the physicalist position promoted by fellows like Dennett.

The weakness of the argument is unfortunate because I find the (reductive/eliminativist) physicalist’s explanation of consciousness risible [3]. I suspect that the argument could be reworked in order to appeal directly to and make use of the sorts of intuitions held by physicalists of a Dennettian sort, all while avoiding the use of modal arguments (“in some possible world…”). This would make for a more effective argument against functionalist/physicalist accounts of consciousness since, at the outset, it gives them everything that they say they want but leads to the necessary abandonment of some of it. What follows, then, is my own version of a zombie thought experiment that, although leaning heavily on the intuitions Chalmers is mining with his zombies, (I think) does a better job.

Building Better Zombies:

Imagine for the moment that there existed a complete neuroscience. I mean ‘complete’ in the sense that this theory ranges over the entire range of properties of neurons as well as their actions and interactions in the terms with which ordinary science is comfortable (i.e. objectively observable/measurable properties) – there is no hint of ‘woo’ about it.  Moreover, this theory has been subjected to rigorous testing and is as good as proven and is able to predict with near perfection what any particular sort of neuron will do whenever any stimuli one would expect to find in its ordinary operational environment (whether biochemical or electrical) are applied to it in said environment [4]. So, were we to have a single neuron placed before us in a petri dish, we should be able to apply any neurotransmitter or electrical charge under any environmental conditions we should choose to subject the cell to, with absolute certainty that it will react in a specific way. This is all well and good, especially since we would not need to make any reference to mental-kind terms (e.g. consciousness, intentionality, representation) – our neuron is simply caused to produce said effect ‘mechanically’, as it were [5]. Indeed, to make any appeal to mental properties at this low level would be to make a claim which no physicalist would suffer gladly – neurons are just too ‘simple’ to be host to intelligence or consciousness.

From this modest beginning, we should be able to attach a second neuron to the first and to apply some stimulus to one or the other and predict with perfect accuracy what each of them will do, considered individually and as a unit. Once again, this prediction will in no way necessitate a resort to mental-kind terms – we are still firmly in the realm of the objectively explicable – and so again with the addition of a third neuron, and a fourth, and a fifth, etc. With each successive neuronal addition, the behaviours of the whole system will become increasingly complex, but without causing any explanatory or predictive troubles (as I have, after all, stipulated that this is a complete neuroscience). On each iteration, we slowly build a neuronal assembly that is increasingly similar to our own human brains until, soon enough, we will have succeeded in building one that is physically and functionally identical to an ordinary human brain which may then be hooked up in the right way to a (presumably custom-built) body. The zombie is ready.

I told you so!

This zombie will now start interacting with its environment and new stimuli will arise naturally from sensory perception of the immediate environment. This will lead to the zombie behaving in complex ways – e.g. using language and planning its vacation to Maui in the fall – based upon the stimuli it receives. Indeed, its behaviour will seem remarkably similar to our own, as we would expect, given that we designed it to be exactly like a neurotypical human being, but for one crucial difference – its behaviours (ranging from thirst to the writing of forlorn love songs) may be explained entirely without reference to mental-kind terms. After all, why should we explain these behaviours by reference to such terms, since they are just the working-out of neuronal cause and effect, which our ideal neuroscience already accounts for with ease?

Not to do so, however, would necessitate accepting some highly dissatisfactory entailments. If our neuroscience really does explain our zombie’s apparently rich range of behaviours, then because we have built a brain that is physically and functionally indistinguishable from that of a womb-born human being [6], we should seek to use the same theory to explain our own behaviour.  Since everything may be satisfactorily explained without need to refer to consciousness, qualia, thought, etc., then explanations of our own activities will also need make no reference to such things.  The trouble is, we emphatically do have subjective experiences and we are conscious. Given this, there are a number of possible moves the physicalist could make:

  1. Give a reductive/eliminative account of phenomena like volition, thought, consciousness, etc. This is, however, precisely what the stipulated ideal neuroscience has done – it has accounted for all higher-order processes in terms of lower-order neurological functioning – and has led only to the present conundrum.
  2. Deny altogether the existence of the referents of mental-kind terms (or, what is the same, insist on their ‘illusoriness’). This strategy preserves the ‘zombic’ quality of our zombie – our mental-kind term-free explanation is then entirely sufficient – but, because our brains are physically and functionally identical to those of the zombie, we necessarily rob ourselves of consciousness, mind, etc.  This, to me, is a major non-starter [7].
  3. Acknowledge the reality of these higher-order phenomena and give a non-reductive account of their emergence from lower-order ones which don’t exhibit mental properties. This preserves the absence of mentality at lower orders of existence, but introduces problems of its own.  Notably, it requires an account of the precise degree of complexity required for emergence to take place.  Furthermore, ‘emergence’ strikes me as something of a scientific equivalent term for ‘and then a miracle happened’.
  4. Abandon physicalism.  There are plenty of acceptable alternatives (dualism, idealism, panpsychism), although they might not be popular in the faculty lounge.


[1] At this juncture I should say that I am only very generally familiar with Dennett’s take on consciousness. Consciousness Explained is on my to-read list, but I haven’t yet got around to it. If I have said something strictly wrong about Dennett’s position, ignorance is my excuse (albeit, a poor one), but if I have got the gist of his position wrong, feel free to take me to task.

[2] He goes on from there to argue for panpsychism, a doctrine with which I shall not concern myself at present (though I find the idea fascinating, if rather counterintuitive and subject to its own problems).

[3] The problems with physicalist accounts of the mind are, to my mind, several and I should like to do a post dedicated exclusively to them, but this is not the time. NB: I do not discount physicalism in its entirety, however, but only those strains of it which claim to already have provided a complete, adequate explanation of the world and everything in it.  The “near enough” physicalism of Jaegwon Kim or Colin McGinn’s physicalist ‘mysterianism’ do not strike me as problematic.

[4] Necessarily, also, in the lab environment. This is, of course, a highly idealized science, but I’m doing philosophy, so I’m able to stipulate anything I wish in order to explore our intuitions. If magical miniature unicorns could do the trick, that would be fair game – so too with scientific theories which require prohibitively complex computations.

[5] Or, rather, biomechanically or biochemically. Or, for that matter, biophysically (especially if quantum minds are something one finds appealing).

[6] I am assuming here that the causal histories of our zombie brain vs. an ordinary human brain will not be relevant, at least insofar as consciousness is concerned – I think it likely that so long as the brain is up and running it should not matter whether it was built in a petri dish or a mother’s belly.  Of course, the different causal histories almost certainly would be of relevance to matters such as personality or learned skills (to name two).

[7] I can’t fathom how it is possible that consciousness (conscious experience) could be an illusion.  For this to be so, it would be necessary that we experience the illusion of having experience.  This idea is so obviously self-defeating and crazy that I wonder why intelligent people go in for it.

The Hard Problem(s) of Minds

The explanatory gap, that is

The 1980-90’s proved to be the decades of consciousness studies in the academic philosophy of mind.  It was during this period in particular that the matters of what consciousness is, whether it exists, and how it is possible were under serious discussion.  Unfortunately, the discipline seems to have moved on to greener pastures since then, but the questions raised during this period are still of the greatest degree of interest.  Probably the most interesting problem raised during this period was that of the ‘hard problem of consciousness’.  The idea here is that consciousness – defined as the very fact of experience, or the ‘what-it-is-like’ to be (and for)\ an experiencing being – cannot be accounted for by appeal to known facts about the material world.  There is an explanatory gap between our physical theories of the world and our lived experience that no collection of data about electron spin or loop quantum gravity seems to be able to bridge.

Of course, there are those who deny that there is a hard problem, insisting instead that the trouble only arises in the minds of people already predisposed towards a dualist outlook.  Dennett, the Churchlands, Hardcastle, and others all are of the opinion that there is no problem, that we have all the conceptual and scientific tools necessary to unravel the knot of consciousness and that refusal to acknowledge this comes from some emotional need to preserve the ‘specialness’ of the mind.  Of course, this is rife psychologizing [1] (and not very compelling, at that) – to say that the Kims or McGinns of the world are predisposed to dualism or trying to save mental ‘specialness’ is a grossly misleading statement that borders on slander.  One could here inject speculations about the sources of the refusals of some to acknowledge the cogency of the case for there being a hard problem, but I shall restrain myself – I am not here for a brawl.

Coming back to the point – how might we get to the hard problem?  [2]

The Weirdness of the Mental

The mind is a really weird thing.  Everything else in the world appears to exhibit certain publicly available properties like mass or spatio-temporal location.  The mind, however, does not have properties like this.  Where, for example, is its location in space?  It might seem like it is in the head, but if much closer attention is paid, it becomes unclear that this is so – sometimes the head seems to be in the mind.  How much space does the mind take up, is it limited or boundless?  If the mind is physical, why does it seem totally unlike all the other stuff we see around us?

The Possibility of Zombies

‘Zombie’ in this context does not refer to the brain-eating undead monsters of the films – rather, we are speaking here about ‘philosophical zombies’.  This sort of zombie is alive, mild-mannered, and doesn’t want your brains because it has its own.  This kind of zombie might live right next door, have a job, wife, mortgage, and kids, and get really excited when it’s playoff season, and you’d never know it was a zombie.  In fact, the only thing this kind of zombie doesn’t have that the rest of us do is consciousness – unlike ordinary humans, there is nothing that it is like to be a zombie.  The point of this sci-fi thought experiment is to demonstrate that because it is conceivable that there could be highly sophisticated cognitive entities that are without consciousness, it is therefore possible that such things could exist and, this being so, the fact of consciousness is difficult to explain.

Building a Better Zombie

If the zombie example seems unconvincing, perhaps that is because we started with a fully formed zombie.  What if we built one from the ground up?  So we take one neuron and study all its actions under various conditions.  Now, we know that whenever chemical c or electrical pulse e is applied under a given condition, the neuron reacts in some specific way, but we don’t imagine that the neuron is conscious.  So we add a second neuron and hook it up in the right way to the first and then apply our chemical or electrical pulse to the first, which reacts in its way and thus causes the second to react in another way.  We still don’t concede that the two neurons are conscious, whether considered individually or collectively.  Then we add a third neuron, then a fourth, then… rinse and repeat.  Since we know what each neuron will do when acted upon in a specified way, eventually we could build a fully functional human brain.  The trick is, since each additional neuron is without consciousness, and we understand perfectly how the entire set-up produces seemingly intelligent responses based on simple stimuli/response action, we would have no reason to make any appeal to consciousness or emotion or any other feature of the mental in describing our new zombie’s activity – it would all simply be the working out of physical cause/effect.  So how are ordinary conscious humans any different?


This is the final problem that I consider a hard problem (or at least sufficiently closely linked to the hard problem to warrant mention here).  Intentionality is the ‘aboutness’ of mental content.  So, for instance, my ‘cat-thoughts’ are about my pet cat, who is just now trying to climb onto my keyboard.  [3]  But intentionality is tricky for two reasons.  Firstly, material objects are not ‘about’ anything at all.  For example, if I see Jesus on my grilled cheese sandwich, the sandwich is not ‘about’ Jesus, I have just made a bunch of hay about a perceived resemblance.  But if my cat-thoughts just are the states of my brain (or some of its subcomponents), how can they anymore be about my cat than the cheese sandwich likeness is about the Lord of Toasts?  Secondly, representation is always of something and to someone, but without consciousness, how can cat-thoughts be represented to anyone (anything)?

These, then, are the ways I think fruitful to construe the hard problem.  I intend in the future to go much more deeply into each of these subjects and, in the interest of disclosure, I am tentatively favourable to the notion that there is a real problem here.  But I am also more than open to go the other way too.


[1] Psychologizing is philosophical bad form, generally.  One ought to deal with one’s opponents’ arguments first – if their arguments are bad or nonsensical, however, then psychologizing may be in order (but only as an error-theory).  By psychologizing their opponents in this way, the individuals listed are in essence saying that one cannot rationally disagree with their general outlook, that disagreement on this point is tantamount to arguing against 2+2=4, or that a thing is not identical to itself.

[2] I have deliberately left what follows sketchy and underdeveloped because I want to leave myself something to write about in the future!

[3] Bad kitty!