Zombie time
by David Large

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More notes from The Great Debate: Being Human

Following Dennett, Caspar has outlined for us four kinds of minded organism, including human beings, that it seems reasonable for us to assume could be produced by natural selection on a planet very much like earth. I’d now like to turn to consider an unminded organism that, arguably, could be produced by natural selection on a planet very much like earth. That unminded organism is the philosophical zombie.

Human beings, zombie beings

Almost everyone agrees that humans share an observable physical aspect and an unobservable (at least by conventional methods) rational aspect. What is distinctive of human beings, as opposed to other organisms, is the human view of the world, the view from where I am, and the view from where I may imagine myself to be. Or to put it another way, it makes sense for us to ask what it’s like to be a human, what it’s like to be me.

Now consider a biological organism that shares all our observable physical aspects but has no rational aspect. Such a thing is what philosophers call a ‘zombie’. Philosophical zombies are not like the undead, and slightly untidy, creatures of the horror movies. The zombies that philosophers’ use in their thought experiments can be exactly like us in all physical respects but have no conscious experiences. There are variations on this definition, but true zombies lack all consciousness, and all self-awareness. There is by definition nothing it is like to be a zombie.

Yet zombies behave like us, spend a lot of time discussing their thoughts and maybe their ‘feelings’, display conscious behaviour, use a rich vocabulary, and may even hold day schools and write books on being human and philosophical zombies. Such disconcerting thoughts help to make vivid the question of what, if anything, is unique about human beings.

Zombies present a special problem for physicalists who believe that human rational, mental life can be explained by, or in terms of, our observable, physical aspects (usually our brains), for there’s no point in producing an account of human nature, in biological or other terms, that simply describes what zombies do. Such a theory would present the neuroscience, the genetics and the evolutionary psychology together with the a priori false claim that this is what it is like to be human.

In other words, though the research may be 100% perfect and 100% complete, the claim to have accounted for being human, and in particular, for what it’s like to be a human would be dead wrong. At best what you’d have would be an account of zombie nature.

The challenge zombies present here is to explain why a so-called biological theory of human nature can ever be more than a theory of zombie nature. There must be a difference, mustn’t there?

Zombie ontology, zombie epistemology

You will have the opportunity to discuss and meet this challenge shortly. First, I’d like to say a little bit more about why there are such a huge number of articles written by philosophers that use the notion of the zombie.

Let me begin by saying that philosophers use zombies for two main purposes:

1) To ask what consciousness is for

If we can imagine a zombie who is, from the outside, indistinguishable from us, who can function exactly as we do, but lacks consciousness, then what on earth do we need consciousness for? What use can it possibly be? Why did it evolve in the first place?

To defend the purposefulness of consciousness against this attack, some philosophers deny that, according to the full and proper definition, it is possible to even imagine a zombie. They think that to be able to behave the way we do, we must be conscious, and therefore to behave the way we do, in it’s full description, we simply must have consciousness. To enforce this point they say, for example, that a zombie could not discuss the function of consciousness without being conscious itself.

On the other hand, philosophers who accept the notion of zombies have to face the consequence that consciousness is thereby rendered seemingly useless. The redundancy of consciousness, thinking, and all meaning-bearing mental activity is referred to as ‘epiphenomenalism’. Epiphenomenlism holds that though humans are conscious, intellectual beings our consciousness and intellect has no meaningful use and is, on most accounts, nothing more than an embarrassing freak of evolution.

Some philosophers who wish to entertain zombies try to get round epiphenomenalism by saying that zombies are imaginable but not possible. Others bite the bullet, accepting both the possibility of zombies and the epiphenomenlogical consequences.

The second main use philosophers have for zombies is:

2) To refute the physicalist, materialist or computational model of the mind

Given the full and proper definition, we may argue that if zombies are physically indistinguishable from us but lack consciousness, then physical properties alone are not sufficient to cause consciousness. This means there is more to consciousness and the mind than the physical world, material items or computational processes.

Unlike 1), with 2) the zombie is indistinguishable not only in behaviour but also in (one or more of) physical structure, materials used and computational algorithm and processing.

Defenders of physicalism, materialism and computationalism attempt to save these theories by claiming that zombies are simply not imaginable. This is the same move as defenders of consciousness in 1), but it does not produce the need to rebut epiphenomenalism. Dennett is a notable adherent of this view, regarding physicalism as true and holding the very notion of the philosophical zombie incoherent. (There’s more to Dennett’s position but this is what it comes to.) A variation on this view holds that the structure of the anti-materialistic zombie argument shows that materialism is conceivable and that this therefore means that zombies are inconceivable!

Now, to be honest, I don’t know anyone who believes that zombies actually exist so why should scientists or anyone other than philosophers worry about this? Well, many people hold that zombies are at least conceivable, and some that they are logically or metaphysically possible. And, as we have seen, if zombies are so much as a bare possibility, then physicalism is false, some kind of dualism is true, and so there can be no complete account of human nature that relies on the biological sciences (such neuroscience, genetics, and evolutionary psychology) alone.

Alongside the ontological conundrums, Zombies also raise epistemological difficulties. In particular, they raise a version of the problem of other minds. If we admit the possibility of zombies then how do I know who (or what) is a zombie and who isn’t a zombie but a human being? Am I addressing an audience of zombies, seemingly appreciative of my every word but in fact non-conscious and oblivious to anything I say or do? How do you, as humans, know that I am not a zombie, delivering these words in the same way as a sentient being? And, perhaps shockingly, if either or both of these scenarios were real, would it matter to us, would it make any difference?

The possibility of zombies

But surely we can’t dismiss the whole of neuroscience, genetics and evolutionary theory as being able to deliver an account of what it is to be human by some made-up story about performing zombies? Well, let’s consider the plausibility of zombies. Perhaps the most powerful argument here is the conceivability argument for zombies. In case you think this is nuts, versions of it have been advanced by such notable philosophers as Saul Kripke, Tom Nagel, David Chalmers, and Joseph Levine. Okay, this may simply serve to confirm your opinion of philosophers but nevertheless here goes:

Zombies are conceivable
Whatever is conceivable is possible
Therefore, zombies are possible

The argument is valid - The conclusion follows from the premises. However, both the premises are problematic. They are unclear as stated, and controversial even when clarified.

A key question is how we should understand ‘conceivable’ in this context. We may hope to avoid the conclusion that zombies are conceivable by appealing to semantic vagueness. On the other hand, the proponents of zombies can make the very same claim - What’s vague for the proponent is vague for the opponent!

Of course we assume that none of us is actually a zombie, and that zombies cannot exist in our world. The central question, however, is not whether zombies can exist in our world, but whether they, or a whole zombie world (which is sometimes a more appropriate idea to work with), are possible in a broader sense. And note, if zombies are conceivable then dualism or non-physicalism is conceivable.

Zombies and evolution

One final point before our discussion: The possibility of zombies seems to pose a problem for evolutionary theory. Why should human beings as creatures with conscious inner lives have survived rather than zombie counterparts of those creatures? Worse, does the seeming evolutionary economy of zombies mean that consciousness is an evolutionary dead end? (We’re back with epiphenomenalism here.) Wouldn’t it be more ‘efficient’ for natural selection to select for zombies rather than human beings? If not then what ecological function or evolutionary purpose could consciousness possibly have?

And this is a serious point. Owen Flanagan and Thomas Polger have claimed that:

‘There are as yet no credible stories about why [conscious] subjects of experience emerged, why they might have won, or should have been expected to win, an evolutionary battle against very intelligent zombie-like information-sensitive organisms’
- O. Flanagan and T. Polger, ‘Zombies and the Function of Consciousness’, Journal of Consciousness Studies, 2, 1995, 313-321.

One response is to suggest that there are as yet undiscovered fundamental biological or psycho-biological laws linking conscious experience to the physical. Such laws, qua laws, would not depend on whether conscious creatures ever happened to evolve. In this case evolution and evolutionary thrift would seem to pose no real threat to the usefulness of consciousness and the meaningfulness of our mental productions. (A version of this response is offered by David Chalmers, see The Conscious Mind, OUP, 1996, p. 171)

But is this what it comes to? In order to preserve the idea that science, in particular neuroscience, genetics and evolutionary psychology, can deliver a proper explanation of consciousness and what it is to be human, do we really have to fall back on a belief in as-yet undiscovered fundamental biological or psycho-biological laws linking conscious experience to the physical? Faith indeed!

At the end of the day, while you may feel able to slant the odds in your favour through careful research, you pays your evolutionary money and you takes your evolutionary chance!

Questions for discussion

1) How can we distinguish between humans and zombies? They can have identical behaviour, structure, history and evolutionary paths, can’t they?
      Note:

• Turing tests and enhanced Turing Tests won’t help distinguish between humans and zombies
• Genetic testing, could do the job, but is premised on having a group of humans and a group of zombies to test in order to first identify a ‘consciousness gene’.

2) How should we respond to epiphenomenalism? Choices include:

• Reject it – If so then what’s so special about being human?
• Embrace it – If so then is consciousness redundant?

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