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Todd Moody’s Zombies

John McCarthy

Computer Science Department

Stanford University

Stanford, CA 94305

jmc@cs.stanford.edu

http://www-formal.stanford.edu/jmc/

1997 Feb 28, 6:24 a.m.

Abstract

From the AI point of view, consciousness must be regarded as

a collection of interacting processes rather than the unitary object

of much philosophical speculation. We ask what kinds of proposi-

tions and other entities need to be designed for consciousness to be

useful to an animal or a machine. We thereby assert that human

consciousness is useful to human functioning and not just and epiphe-

nomenon. Zombies in the sense of Todd Moody’s article are merely

the victims of Moody’s prejudices. To behave like humans, zombies

will need what Moody might call pseudo-consciousness, but useful

pseudo-consciousness will share all the observable qualities of human

consciousness including what the zombie will be able to report. Robots

will require a pseudo-consciousness with many of the intellectual qual-

ities of human consciousness but will function successfully with few if

any human emotional conscious qualities if that is how we choose to

build them.

Introduction

From the AI point of view, consciousness must be regarded as a collection

of interacting processes rather than the unitary object of much philosophi-

cal speculation. We ask what kinds of propositions and other entities need

to be designed for consciousness to be useful to an animal or a machine.

We thereby assert that human consciousness is useful to human functioning

and not just and epiphenomenon. Zombies in the sense of Todd Moody’s

article are merely the victims of Moody’s prejudices. To behave like hu-

mans, zombies will need what Moody might call pseudo-consciousness, but

useful pseudo-consciousness will share all the observable qualities of human

consciousness including what the zombie will be able to report. Robots

will require a pseudo-consciousness with many of the intellectual qualities of

human consciousness but will function successfully with few if any human

emotional conscious qualities if that is how we choose to build them.

Such is an AI doctrine on the subject. We now must ask what are the

specific processes that make up the consciousness necessary for successful

robots and the additional processes required should we want them to imitate

humans. Many aspects of intelligent behavior do not require anything like a

human level of consciousness, and hardly any AI systems built so far have

any. For this reason the following remarks are somewhat speculative and

are more stimulated by people like the Dreyfuses and Penrose who deny the

possibility of robot consciousness than by any features of existing programs.

We regard consciousness as a subset of the memory of an animal or ma-

chine distinguished by the fact that many processes involve only those ele-

ments of memory that are in consciousness. The elements of memory include

propositions (like sentences) and other entities We may divide our consider-

ation into basic consciousness and consciousness of self.

2 Basic Consciousness

Here are some of the elements of basic consciousness.

propositions The propositions of basic consciousness are about the world

and not about the system’s thoughts. There is a gray area, and, for

example, a proposition that the system is hungry can be looked at the

other way.

images of scenes and objects These may be either remembered images

or images of objects currently being sensed. By image, I do not mean

merely two dimensional visual images such as those projected on the

retina. Included are auditory images and three dimensional images of

objects. The auditory images of speech are transformed by filters char-

acteristic of the hearer’s understanding of the language. The images

of three dimensional objects involve vision, touch and also experience

with the particular kind of object.

Much more can be said about images, but it is inessential for this

review, except to make the point that the actual details are important

in understanding consciousness.

3 Consciousness of Self

[McC95] discusses the kinds of consciousness of its own mental processes a

robot will require in order to behave intelligently. Here are a few of them.

  1. Keeping a journal of physical and intellectual events so it can refer to its past beliefs, observations and actions.
  2. Observing its goal structure and forming sentences about it. Notice that merely having a stack of subgoals doesn’t achieve this unless the

    stack is observable and not merely obeyable.

  3. The robot may intend to perform a certain action. It may later infer that certain possibilities are irrelevant in view of its intentions. This

    requires the ability to observe intentions.

  4. Observing how it arrived at its current beliefs. Most of the important beliefs of the system will have been obtained by nonmonotonic rea-

    soning, and therefore are usually uncertain. It will need to maintain

    a critical view of these beliefs, i.e. believe meta-sentences about them

    that will aid in revising them when new information warrants doing so.

    It will presumably be useful to maintain a pedigree for each belief of

    the system so that it can be revised if its logical ancestors are revised.

    Reason maintenance systems maintain the pedigrees but not in the

    form of sentences that can be used in reasoning. Neither do they have

    introspective subroutines that can observe the pedigrees and generate

    sentences about them.

  5. Not only pedigrees of beliefs but other auxiliary information should either be represented as sentences or be observable in such a way as

    to give rise to sentences. Thus a system should be able to answer the

    questions: “Why do I believe p?” or alternatively “Why don’t I believe

    p?”.

  6. Regarding its entire mental state up to the present as an object, i.e. a context.

    [McC93] discusses contexts as formal objects. The ability

    to transcend one’s present context and think about it as an object

    is an important form of introspection, especially when we compare

    human and machine intelligence as Roger Penrose (1994) and other

    philosophical AI critics do.

  7. Knowing what goals it can currently achieve and what its choices are for action. We claim that the ability to understand one’s own choices

    constitutes free will. The subject is discussed in detail in [MH69].

    Taken together these requirements for successful human-level goal achiev-

    ing behavior amount to a substantial fraction of human consciousness. A

    human emotional structure is not required for robots.

    4 Moody Zombies

    Moody isn’t consistent in his description of zombies. On the page 1 they

    behave like humans. On page 3 they express puzzlement about human con-

    sciousness. Wouldn’t a real Moody zombie behave as though it understood

    as much about consciousness as Moody does?

    References

    [McC93] John McCarthy. Notes on formalizing context. In IJCAI-93, 1993.

    Available on http://www-formal.stanford.edu/jmc/.

    [McC95] John McCarthy.

    states.

    tal

    formal.stanford.edu/jmc/.

    1995.

    Making robots conscious of

    their men-

    to appear, available on http://www-

    [MH69] John McCarthy and Patrick J. Hayes. Some philosophical prob-

    lems from the standpoint of artificial intelligence.

    In B. Meltzer

    and D. Michie, editors, Machine Intelligence 4, pages 463–502. Ed-

    inburgh University Press, 1969.

    /@sail.stanford.edu:/u/jmc/e95/zombie1.tex: begun 1995 Jul 30, latexed 1997 Feb 28 at 6:24 a.m.