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Are YOU Conscious?

Posted by Zombie on 24 October 1999, at 1:50 a.m.

Zombies are hypothetical creatures of the sort that philosophers have been known to cherish. A zombie is physically identical to a normal human being, but completely lacks conscious experience. (Here is a brief case-study .) Zombies look and behave like the conscious beings that we know and love, but "all is dark inside." There is nothing it is like to be a zombie.

(Note that these zombies need to be distinguished from Hollywood zombies and Haitian voodoo zombies, which typically have behavioral impairments and may have some sensory experiences. They are also not to be confused with the drink, the Unix process, or the 1960s pop group.)

Very few people think that zombies could exist in the actual world (i.e., that they are naturally or nomologically possible), but many people think that they are at least logically possible - i.e. that the idea of zombie is internally consistent, and that there is at least a "possible world" where zombies exist. This logical possibility is sometimes used to draw strong conclusions about consciousness (e.g. in my book The Conscious Mind, and elsewhere).

For example:

It can be used as a way of illustrating the "hard problem" of consciousness, which might be phrased as the question of "why aren't we zombies". If any account of physical processes would apply equally well to a zombie world , it is hard to see how such an account can explain the existence of consciousness in our world.

It can be used to raise questions about the function of consciousness: why did evolution bother to produce us if zombies would have survived and reproduced just as well? (As e.g. Flanagan and Polger [1995] have argued.)

And it can even be used to argue against materialism: if there is a possible world which is just like this one except that it contains zombies, then that seems to imply that the existence of consciousness is a further fact about our world. To put it metaphorically, even after determining the physical facts about our world, God had to "do more work" to ensure that we weren't zombies.
The general point is that the logical possibility of zombies is one way of illustrating that there is no logical entailment from physical facts to facts about consciousness, whereas there is such an enatilment in most other domains. Of course even the logical possibility of zombies is controversial to some (e.g. Dennett [1995]), as conceivability intuitions are notoriously elusive; and some scientists have been known to wonder whether anything important really follows from what is merely conceivable. I think that most arguments that use zombies can actually be rephrased in a zombie-free way, so that these arguments can be set aside if one prefers; but zombies at least provide a vivid and provocative illustration.

(A related idea is that of a functional isomorph of a normal human that lacks conscious experience: perhaps a system with silicon chips instead of neurons, for example. This has occasionally been called a "functional zombie", though usually it goes by the more prosaic name of "absent qualia". Some use the logical possibility of such a functional zombie to argue against reductive functionalist theories of consciousness. Of these, some go further and argue that functional zombies might even exist in the actual world, suggesting that any form of functionalism or AI is doomed. Others (like me) deny this, so that the mere logical possibility of zombies doesn't stand in the way of AI.)

As far as I know, the first paper in the philosophical literature to talk explicitly and at length about zombies was Robert Kirk's "Zombies vs. Materialists" in Mind in 1974, although Keith Campbell's 1970 book Body and Mind talks about an "imitation-man" which is much the same thing. After that, there was hardly any explicit discussion of zombies in the philosophical literature for a long time (although there was quite a lot on "absent qualia", i.e. functional zombies). When I wrote my 1993 Ph.D. thesis. in which zombies played a central role, there was hardly anything out there. But for one reason or another, zombies have risen from the grave in the last couple of years; and they turn out to be unaccountably well-represented on the web, in particular.

So here are a few links for the zombieholic.

Papers on zombies:

Selmer Bringsjord (1995), "In defense of impenetrable zombies"
A commentary on Moody 1995 (one can't really distinguish zombies and humans).
http://www.rpi.edu/~brings/SELPAP/zombies.jcs/zombies.jcs.html

Selmer Bringsjord (1996), "The zombie attack on the computational conception of mind" Using the possibility of zombies to draw out inconsistencies in Dennett's argument against Searle.
http://www.rpi.edu/~brings/SELPAP/zombies.ppr/zombies.ppr.html

David Chalmers (1993), "Self-ascription without qualia: A case-study"
A commentary on a paper by Goldman, with a case-study of "Zombie Dave".
http://ling.ucsc.edu/~chalmers/papers/goldman.html

David Chalmers (1995), "Absent qualia, fading qualia, dancing qualia"
Thought-experiments about functional isomorphs, arguing that in the actual world such isomorphs will be conscious.
http://ling.ucsc.edu/~chalmers/papers/qualia.html

David Chalmers (1996), "The Conscious Mind: In Search of a Fundamental Theory"
My book on consciousness, with all the zombie discussions you could ever ask for. Unfortunately most of the zombie stuff isn't available on the web.
http://ling.ucsc.edu/~chalmers/tcm.html

Allin Cottrell (1996), "On the conceivability of zombies: Chalmers v. Dennett"
A thoughtful paper arguing that zombies as I describe them in my book may not really be conceivable.
http://www.wfu.edu/~cottrell/zombies.ps

Daniel Dennett (1995), "The unimagined preposterousness of zombies"
Zombies aren't really imaginable.
http://ase.tufts.edu/cogstud/papers/unzombie.htm

Owen Flanagan & Tom Polger (1995), "Zombies and the function of consciousness"
Using zombies to question whether consciousness has a function.
http://www.duke.edu/~twp2/zombies.html

Stevan Harnad (1995), "Why and how we are not zombies"
The epistemic possibility of zombies illustrates the limits of cognitive science.
ftp://ftp.princeton.edu/pub/harnad/Harnad/HTML/harnad95.zombies.html

Larry Hauser (1995), "Revenge of the zombies"
Uses "good zombies" to fight the "evil zombies" of dualism & identity theory, yielding behaviorism. http://members.aol.com/lshauser/zombies.html

Jaron Lanier (1995), "You can't argue with a zombie"
Dennett & other consciousness skeptics and AI supporters must be zombies.
http://www.well.com/user/jaron/zombie.html

Peter Marton (1998), "Zombies vs. materialists: The battle for conceivability"
Zombies are conceivable if and only if materialism is inconceivable.
http://www.brown.edu/Departments/Philosophy/zombie.html

Todd Moody (1995), "Conversations with zombies"
Zombies will be distinguishable as they won't worry about consciousness.
http://www.imprint.co.uk/Moody_zombies.html

Nigel Shardlow, "Zombies"
Zombie behavior would be coincidental or lying; the idea rests on a Cartesian conception of self-knowledge.
http://ds.dial.pipex.com/town/close/xdr88/zombies.htm

Nigel Thomas (1996), "Zombie Killer"
Zombies would claim to be conscious, and this leads to an incoherence. Whether the claim is interpreted as true, false, or meaningless, trouble for the zombiephile results.
http://www.calstatela.edu/faculty/nthomas/zom-abs.htm

Other philosophical zombie resources:

Journal of Consciousness Studies zombie symosium.
http://www.imprint.co.uk/jcs_2_4.html

Larry Hauser's zombie page.
http://members.aol.com/lshauser/zomboid.html

Selmer Bringsjord's zombie page.
http://www.rpi.edu/~brings/SELPAP/ZOMBIES/zomb.htm

Zombie discussions on PSYCHE-D (run a find on "zombie")
http://www.ai.sri.com/~connolly/psyche-list/index.html#254

Zombies and modal arguments (from my philosophy of mind bibliography)
http://ling.ucsc.edu/~chalmers/biblio1.html#1.3b

Experts speak out on the zombie threat
http://www.teleport.com/~oro/zombie/zexperts.html
(Zombie Alert commentary on the above papers:
http://www.teleport.com/~oro/zombie/index.html)

--Thanks especially to Larry Hauser and his zombie page for giving me the idea.

David Chalmers

[The author of this article is a philosopher, now teaching at the University of Arizona. His webpage is http://ling.ucsc.edu/~chalmers/]

Responses

• Re: Are YOU Conscious? - George - 7 December 1999, at 1:24 p.m.

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