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Imagining zombies

Understanding the relationship between the mind and the body remains one of the most vexed problems in philosophy, cognitive science, and neuroscience. Throughout much of the last hundred years, physicalism has been the orthodox position in the philosophy of mind. Physicalist views share the characteristic attitude that mental phenomena — such as beliefs, desires, experiences and emotions — are either nothing but physical phenomena — brain states, say — or are in some important sense accounted for or made real by physical phenomena.

Physicalism has not reigned unchallenged, however. A number of arguments have been raised which promote dualism in its place — the view that fundamentally, the mind and body are separate, and mental phenomena can never be adequately characterised in terms of physical goings-on.

Perhaps the most prominent and widely discussed of these is the ‘Zombie Argument’, developed and defended by David Chalmers over the past twenty-five years or so — although the line of thought behind it goes back at least as far as Descartes.

Chalmers’ argument focusses on one particular aspect of mental phenomena – phenomenal experience or that-which-it-is-like to undergo a particular mental process or to be in a particular mental state, such as:

“… the felt quality of redness, the experience of dark and light, the quality of depth in a visual field … the sound of a clarinet, the smell of mothballs… bodily sensations from pains to orgasms; mental images that are conjured up internally; the felt quality of emotion … the experience of a stream of conscious thought.” (Chalmers, 2010)

In motivating the argument, Chalmers asks us to consider creatures that he calls ‘zombies’ — not these ones! — which are physically identical to human beings but which lack all phenomenal experience. For all the similarity of a zombie’s behaviour to ours, when a zombie peers out into the gradually darkening red-hued sunset; inhales the musty smell of her closet whilst strains of her daughter’s clarinet practice come screeching through the wall; when she cries out wildly due to the touch of a red hot poker, or that of her lover, and so on … there is nothing that it is like to be her. In other words, none of this is accompanied by phenomenal experience.

Zombies may well inhabit zombie worlds; worlds that are complete physical duplicates of our own, but without any phenomenal experiences occurring there. In such a world, for example, your ‘zombie twin’ is currently sat reading about zombies, just as you are, but there is nothing it is like for your zombie twin to do so.

‘Mr Pipo thoughts’, by Nevit Dilmen. CC BY-SA 3.0 via Wikimedia Commons.

The key to the zombie arguments is the following line of thought: if zombies are possible then physicalism must be false. This is because if all the physical features of a human have been duplicated and there’s still something missing as far as mentality goes, then whatever’s missing can’t be physical: if it were, it wouldn’t be missing! If it can be argued that zombies are possible, then it looks like a good argument against physicalism is in the offing.

The simplest version on Chalmers’s argument runs as follows:

(P1): Zombies are conceivable

(P2): Whatever is conceivable is possible

(C): Zombies are possible

The argument is valid: if the premises (P1) and (P2) are both true, then the conclusion, (C), follows. So any response to the argument ought to target the truth of one of the premises. Typically, those responding to the argument have accepted the first premise, that we can conceive of zombies, but have questioned the second, arguing that whether or not we are able to imagine or conceive of something isn’t a good guide to whether or not that thing is possible.

However, it’s far from clear whether (P1) is in fact true: that is, whether or not we can really conceive of zombies. To see why, it’s easiest to consider some related things we clearly can conceive of, but which don’t live up to the aspirations of (P1). For instance, we can form a picture a human being in our heads, and say to ourselves ‘and it doesn’t have any phenomenal experience’. But this is far from conceiving of an exact physical duplicate of a human which lacks phenomenal experience.

Here’s an analogy, think of a mechanical clock, indeed, an exact duplicate of a mechanical clock you’re acquainted with. Can you conceive of the duplicate’s hands running anti-clockwise, rather than clockwise, or not running at all? You certainly could form a mental picture of the clock and say ‘and the hands run backwards’. But under close inspection, it’s not clear one could maintain this picture under scrutiny without making some change to the clock — say by rearranging the gears, or changing the direction of the motion imparted by the motor.

Additional pressure can be put on the notion of conceivability when one realises that things which are conceivable individually aren’t always conceivable in combination. Think about the following mathematical case: Goldblach’s conjecture says that every even integer greater than 2 can be expressed as the sum of two primes. Whilst we know the conjecture holds up to very large numbers, it remains unproven: given all our evidence, it could be true or it could be false. So it seems that individually, we can conceive of Goldblach’s conjecture either being true or of it being false: but we can’t conceive of both together, of its being both true and false. The contradiction here is obvious.

What about the zombie case? Well, it’s clear we can conceive of the notion of ‘an exact duplicate of a human being’, and, separately, of the notion of ‘lacking phenomenal experience’. Conjoining the two doesn’t lead to an obvious contradiction, like in the Goldblach case. But it is far from obvious, given our relative lack of knowledge of the relationship between the mind and the body, whether or not a contradiction lies waiting to be unearthed in the notion of zombie. Without further information on the nature of the brain, of mentality, and of the sorts of features we take to typify each, assent to (P1) should be withheld.

Featured image credit: ‘Scary Landscape Reflections’, by Leon Fishman. CC BY 2.0 via Flickr.

Recent Comments

  1. 'Trick Slattery

    Great job. My position on this philosophical “zombie” matter is similar if not identical:

    Philosophical Zombies? Inconceivable!

  2. Dr Andrea Christofidou

    It’s depressing to see Descartes being dragged into any view that anyone has about the mind and body. First, for Descartes, mind and body are *not* separate; they are really distinct — that is, they are metaphysically distinct kinds of entity. His argument for dualism is an argument for the Real Distinction between mind and body. “Real Distinction” does not mean actual separation, but only separability — a mere logical possibility of separateness.

    Secondly, for Descartes, conceiving is not the same as imagining. He clearly distinguishes between the two and defends the difference with good arguments. In contemporary discussions the two notions are too often run together without, it seems, any awareness of the difference between them.

    Thirdly, for Descartes, it is not our conception that makes something thus and so; rather, our conception is constrained by the nature or essence of the thing itself. That is, what we conceive clearly and distinctly is the nature or essence of the thing/entity in question.

    Fourthly, the nature or essence of body is extension, but for Descartes, the human body must have, in addition, “all the dispositions required to receive a mind […] to be strictly a human body […] indeed, [there is] a natural requirement […] of an appropriate positioning and arrangements of various parts”. [Letters to Regius December 1641, and January 1642, respectively.]

    Fifthly, the nature or essence of mind is thinking, in the broad sense — that is, consciousness. The mind has no parts, though it has faculties and modifications (i.e., individual mental states). Thoughts, feelings, pains, desires, hopes, fears, and so on, do not have shape, size, colour, smell, or taste. What it is to be a human being, a person, for Descartes, is to be a substantial union of the self/mind and the human body.

    Whether zombies are possible or not, has nothing to do with Descartes’ argument for dualism.

  3. Alex C

    Trick – thanks, glad you enjoyed it

    Andrea – thanks for reading and for taking the time to comment. I agree with much of what you say about Descartes, and I’m sure others will get a lot out of your comment too!

    My point was simply that there’s at least a family resemblance between Descartes a line of thought that comes up in the sixth meditation (that what man can conceive, God can actualise) and that at play in the zombie argument – both begin with an epistemic premise, strengthen this with something that links conceivability and genuine possibility, in service of drawing dualist conclusions. This line of thought may not be representative of the final, considered Cartesian opinion, but it’s present in the text.

    In the context of academic philosophy, you’re right of course about subtle distinctions between conception/imagination and separateness/distinctness – but in a short piece written to with a view to piquing the interest of a generalist audience, I think these terms can be treated as close to synonymous.

    Also, I think it’s a little unfair to suggest that in contemporary philosophy of mind little attention is paid to being precise about conceivability etc. – Chalmers for one has written plenty making clear different senses of conceivability and which of those he has in mind.

  4. Andrea

    Alex – thank you for your response, and I am pleased that you agree with much of what I say about Descartes. A few points to clarify:

    First, even if your article is meant for a general audience, it seems to me that it’s important to present crucial distinctions correctly (especially, given the misconceptions that are perpetuated even by professional philosophers). I guess we wouldn’t think that if a short piece is for a general audience, we can say that a right-angled triangle is synonymous with an isosceles triangle.

    Secondly, the argument in the Sixth Meditation is based “in an order corresponding to the actual truth of the matter”; it is an argument concerning the nature or essence of things. It is not an epistemological argument; arguments of that sort, found in the Second Meditation, are based “in an order corresponding to [the meditator’s] own perception” (see Preface to the Reader AT VII 8) and therefore the meditator does not derive any metaphysical conclusions from them – he is fully aware of such fallacies. Nor does he argue from doubt, or from ignorance but proceeds by making judgements only about things which are known to him (AT VII 27).

    Thirdly, as I said previously, for Descartes the direction of reasoning is from the nature or essence of things to our thought or conception. He argues that the mind is distinct from body, and distinct not by an abstraction of the intellect, but that it can be known as a distinct thing because it is in reality distinct.
    The nature or essence of things is the source, not a consequence of our conception, or indeed of the signification and usage of our terms (see AT VII 176).

    I’m not sure which direction of reasoning Chalmers’ view of conceivability follow (and doesn’t he sometimes use it interchangeably with imagining?).

  5. David J Chalk

    Hi Alex, thanks for the very interesting blog post.

    I realize there are perhaps some finer points regarding zombies that I haven’t grasped but I’d like to offer this. Granted, a clock won’t run backwards without a physical change. But doesn’t this simply say that we can’t have a physical change without a physical change? I don’t understand how it gets to the point of the issue regarding conceivability.

    In his book, “The Conscious Mind” (pg 96), Chalmers says, “The idea of zombies as I have described them is a strange one. For a start, it is unlikely that zombies are naturally possible. In the real world, it is likely that any replica of me would be conscious. … But the question is not whether it is plausible that zombies could exist in our world, or even whether the idea of a zombie replica is a natural one; the question is whether the notion of a zombie is conceptually coherent.”

    So Chalmers would agree that a zombie who is molecule by molecule identical to a person is unlikely to be naturally possible. This would follow from the mind supervening on the physical.

    I believe one can imagine, and it is perfectly conceivable (ie: does not violate any physical laws / laws of nature as we know them today) to imagine a person, identical in every way to a person today, who has no phenomenal consciousness. For this to be true, we should first, be able to imagine examining every physical fact about a person without the need to resort to explaining phenomenal consciousness, and those physical facts should, in principal, provide sufficient explanation about the person to describe everything that can be observed or measured. Second, if this examination was of a zombie, we should find that this examination was identical to a person having a phenomenal experience and we should not find any physical laws being violated. Therefore, if a complete, physical description does not discern the difference, then zombies are conceivable.

    Best regards,

  6. VicP

    The zombie argument is interesting but also an example of intellectual arrogance or an intellectual category error. Most philosophical thinkers are no better equipped mentally than Descartes was centuries ago understanding something as technical as the human brain. From my engineering background this reminds me of a car salesman trying to sell you an auto based on a use of technical terms but absolutely no understanding of automotive engineering. The zombie conjecture is a classical example of how we have fallen victim to the advertising fallacy, which we also see in the media control of zombie politics.

  7. Andrea

    Andrea writes:
    In reply to VicP I should like to say that the intellectual category mistake is committed by physicalism in all its various guises. Physicalism is based on an unargued premise that everything is ontologically physical and therefore tries to fit in that view, thought and consciousness but, unsurprisingly, without any success. After more than 100 years of physicalism, we’re none the wiser concerning these problems. The reason for this is because the problem (it’s a problem for physicalism) of the mind or consciousness is a metaphysical problem, that is, it has to do with the true nature of mind; it is not simply an epistemological problem as we’re (mis)led to believe by physicalists. At most what physicalist writers and thinkers have achieved over the last 100 years are more and more technicalities without any philosophical substance or real philosophical reflection.
    As Descartes clearly understood the mind is itself natural and it is guided by the natural light of reason. There is nothing supernatural or elusive about it. He clearly understood: “The fact that thought [broadly construed] is often impeded by bodily organs [e.g., the brain], as we know from our own frequent experience, does not at all entail that it is produed by those organs. This latter view is one for which not even the slightest proof can be adduced.” (AT VII 228)
    Physicalism has neither produced nor can it produce the slightest proof because the nature of the brain is distinct from the nature of the mind. The former is extended, it has at least shape and size. The latter, the mind is conscious — it has no shape or size; it’s a category mistake to think that our thoughts are triangular, green or blue, or that our pains are square, red or yellow. The mind has phenomenology — there is something it is like to be, say, in pain; the brain hasn’t. The mind has intentionality — it’s directed towards something independent of itself; the brain isn’t — it has synapses, neurons firing. The mind or consciousness is essentially connect with a point of view, or a first-person point of view; the brain isn’t. In the case of beings like us, the mind is not simply conscious but self-conscious; it has reflection and understanding; the self essentially connected with the mind has the ability to consider itself as itself, to consider the possibility of its autonomy and freedom.
    As Descartes clearly and distinctly understood “the mind is distinct from the body [the brain], and distinct not just by a fiction or abstraction of the intellect: it can be known as a distinct thing because it is in reality distinct.” (AT VII 229)

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