Lecture Nine - PowerPoint Presentation

Slide1

Lecture Nine

The Zombie Argument

人

皮囊论证Slide2

The most famous philosopher who put forward the zombie argument

David

John Chalmers

 (born 20 April 1966) is an 

Australian

philosopher

specializing

in the area of 

philosophy of mind

 and 

philosophy of language

, whose recent work concerns 

verbal disputes

. He is Professor of Philosophy and Director of the Centre for Consciousness at the 

Australian National University

. He is also Visiting Professor of Philosophy at 

New York University

.Slide3

What does philosophical Zombie mean?

A 

philosophical 

zombie

 or 

p-zombie

 in the 

philosophy of mind

 and 

perception

 is a hypothetical being that is indistinguishable from a normal human being except in that it lacks 

conscious experience

, 

qualia

, or 

sentience

.

[1]

When a zombie is poked with a sharp object, for example, it does not feel any pain though it behaves exactly as if it does feel pain (it may say "ouch" and recoil from the stimulus, or tell us that it is in intense pain).Slide4

In what sense does the idea of Zombie make troubles for physicalism

?

1.

Physicalism

is the view that

the physical

world

is all there is. If they are right, then other true factual statements are 

nothing but the re-description of the physical. Think about how the God created the world in a

physicalist

framework.

2. So if

physicalism

is right, accounts for consciousness should be re-descriptions of the physical.

3. There should be Zombies, whose physical properties are like normal persons, but lacking consciousness.

4. So from the physical perspective, the absence of consciousness makes explanatory problem for

physicalism

. Or in other words, there is a “explanatory gap” between having the physical and lacking the mental.

5. Therefore,

physicalism

is false. Slide5

A Terminological Problem: What is consciousness?

Here consciousness means “qualia”.

Qualia

 ( 

/ˈ

kwɑːliə

/

 or 

/ˈ

kweɪliə

/

), singular "

quale

" (Latin pronunciation: 

[ˈ

kwaːle

]

), from a 

Latin

 word meaning for "what sort" or "what kind," is a term used in 

philosophy

 to refer to subjective 

conscious

 experiences as 'raw feels

'.Slide6

The conceivability argument for the possibility of zombies

1.Zombies

are conceivable.

2.Whatever

is conceivable is possible.

3.Therefore

zombies are possible

.

Or more technically,

1. Zombies are conceivable in some thought experiments.

2. Whatever exits in a thought experiment exists in a possible world.

3. Therefore there are zombies in some possible worlds.

It is important to remember that

physicalism

cannot hold if zombie exits in even one possible world. Slide7

The first problem: Are zombies conceivable?

Chalmers

finds

the conceivability of zombies ‘obvious’: he remarks that ‘it certainly seems that a coherent situation is described; I can discern no contradiction in the description’ (1996, p. 96). However,

intuition is something that cannot

be relied

on in philosophy. We need more detailed justifications.Slide8

Argument for the conceivability （1

）

Suppose a person

is progressively being deprived of qualia in one sense modality

(

感官道

) after

another, even though most of the time he continues to produce behavior that would have been appropriate if he had retained full consciousness. As soon as all his sense modalities have been affected, his patterns of behavior revert to normal; but the suggestion is that it is at least intelligible to say he has become a zombie (Kirk 1974a).

EVALUATION:

However

, this line of reasoning falls well short of establishing that zombies are really conceivable. It seems to depend on much the same cluster of intuitions as the original idea.Slide9

Argument for the conceivability （2

）

Another thought experiment involves a team of

micro-Lilliputians(

小人国成员

)

who invade

Gulliver‘s head

（格列佛的脑袋）

,

disconnect his

afferent

（感受的）

and

efferent

（效应的）

nerves, monitor the inputs from his afferent nerves, and send outputs down his efferent nerves to produce behavior indistinguishable from what it would have been originally. The resulting system has the same behavioral dispositions as Gulliver but (allegedly) lacks sensations and other experiences, contrary to the ‘Entailment Thesis’, according to which the physical facts entail the psychological facts (Kirk 1974b

).

Slide10

Argument for the conceivability （3

）

Suppose a population of tiny people disable your brain and replicate its functions themselves, while keeping the rest of your body in working

order;

each homunculus

（小人）

uses

a cell phone to perform the signal-receiving and -transmitting functions of an individual neuron. Now, would such a system be conscious? Intuitively one may be inclined to say obviously not. Some, notably functionalists, bite the bullet and answer yes. However, the argument does not depend on assuming that the homunculus-head would not be conscious. It depends only on the assumption that its not being conscious

is

conceivable

 — which many people find reasonable. In Chalmers's words, all that matters here is that when we say the system might lack consciousness, ‘a meaningful possibility is being expressed, and it is an open question whether consciousness arises or not’ (1996, p. 97). If he is right, then the system is not conscious. In that case it is already very much like a zombie, the only difference being that it has little people where a zombie has neurons. Slide11

Argument against the conceivability

（

1

）

According

to

verificationism

(

证实主义

),

a (declarative) sentence is meaningful just in case its truth value can be verified. This entails that unverifiable sentences are literally meaningless, so that no metaphysical claim according to which unobservable nonphysical items exist can be true. However, since our ability to think and talk about our experiences is itself a problem for

verificationism

, to presuppose it when attacking the zombie idea would beg the question. 

Or in another way, “Zombies are conceivable” is meaningless because the very statement

cannot be verified.Slide12

Argument against the conceivability （

2

）

The second idea is Wittgenstein's ‘

private language argument

’. Although not crudely

verificationistic

, it depends on the assumption that in order for words to be meaningful, their use must be open to public checking. If sound, therefore, it would seem to prove that we cannot talk about qualia in the ways that defenders of the zombie possibility think we can; the

checkability

assumption therefore also seems question-begging in this context.

Or in another way, “Zombies are conceivable” is meaningless because the very statement

is not checkable in the public square. So, it should be someone’s private language. But Wittgenstein has told us that private language is impossible.Slide13

Argument against the conceivability (3)

According to the third idea, 

behaviorism

, there is no more to having mental states than being disposed to behave in certain ways. As a possible basis for attacking the zombie idea, behaviorism is in a similar situation to

verificationism

and the private language argument. Obviously zombies would satisfy all behavioral conditions for full consciousness, so if we could know a priori that behaviorism was correct, zombie worlds would be inconceivable for that reason. Slide14

Argument against the conceivability

(4)

A much more widely supported approach to the mental is 

functionalism

: the view that mental states are not just a matter of behavior and dispositions, but of the causal or other ‘functional’ relations of sensory inputs, internal states, and behavioral outputs. (Note that unless the nature of the internal processing is taken into account as well, then functionalism falls to most of the usual objections to behaviorism, for example to the ‘homunculus-head’ described in the last section.) Since zombies would satisfy all the functional conditions for full consciousness, functionalism entails that zombies are impossible. Of course functionalism cannot just be presupposed when attacking the zombie idea: that would hardly be any better than presupposing behaviorism. But increasingly sophisticated versions of functionalism are being formulated and defended today, and any arguments for functionalism are

a fortiori

arguments

(

“更何况论证”

)

against the possibility of zombies

.

NOTE:

The Latin phrase 

argumentum a fortiori

 denotes "argument 'from [the] stronger [reason]'." For example, if it has been established that a person is deceased, then one can, with equal or greater certainty, argue that the person is not breathing.Slide15

Argument against the conceivability (5)

1. Suppose that zombies are conceivable.

2. A fortiori, possible worlds in which qualia are nothing but

epiphenomenal qualia

are conceivable (if the stronger thesis holds, the weaker one does as well). That is to say, people there do have qualia (in this sense they are not zombies), but the qualia do not have any causal power , or

causally inert

(in this sense these persons are similar to zombies).

3. So in these worlds, people cannot have any ‘epistemic

contact’ with those

experiences or qualia.

4. So these epiphenomenal qualia contribute nothing to people’s mental life.

5. But by definition, e-qualia are accessible to people. Being known is some causal relationship.

6. (5) contradicts (4).

7. Hence, epiphenomenal worlds are not conceivable.

8. Therefore, zombies are not conceivable .(If the weaker thesis cannot hold, the stronger cannot as well.)Slide16

The second problem: Does conceivability entail possibility?

A number of philosophers argue that

Kripke‘s

ideas about

a posteriori necessary truth

(

后验必然真理

)

facilitate

the defense of

physicalism

. They urge that even if a zombie world is conceivable, that does not establish that it is possible in the way that matters.

Conceivability is an epistemic notion

, they say, while

possibility is a metaphysical one

: ‘It is false that if one can in principle conceive that P, then it is logically possible that P; … Given psychophysical identities, it is an ‘a posteriori’ fact that any physical duplicate of our world is exactly like ours in respect of positive facts about sensory states’Slide17

MORE ON THIS:

Saul Aaron

Kripke

 (born November 13, 1940) is an 

American philosopher

and

logician

. He is a professor 

emeritus

 at 

Princeton

 and teaches as a Distinguished Professor of Philosophy at the 

CUNY Graduate Center

. Since the 1960s

Kripke

has been a central figure in a number of fields related

to

mathematical

logic

, 

philosophy of language

, 

philosophy of

mathematics

,

metaphysics

, 

epistemology

, and 

set theory

.Slide18

MORE ON THIS:

The metaphysical distinction between necessary and contingent truths has also been related to 

a priori

 and a posteriori

 knowledge. A proposition that is 

necessarily true

 is one whose negation is self-contradictory (thus, it is said to be true in every 

possible world

). Consider the proposition that all bachelors are unmarried. Its negation, the proposition that some bachelors are married, is incoherent, because the concept of being unmarried (or the meaning of the word "unmarried") is part of the concept of being a bachelor (or part of the definition of the word "bachelor"). To the extent that contradictions are impossible, self-contradictory propositions are necessarily false, because it is impossible for them to be true. Thus, the negation of a self-contradictory proposition is supposed to be necessarily true. By contrast, a proposition that is 

contingently true

 is one whose negation is not self-contradictory (thus, it is said that it is 

not

 true in every possible world). As Jason

Baehr

states, it seems plausible that all necessary propositions are known 

a priori

, because "[s]

ense

experience can tell us only about the actual world and hence about what is the case; it can say nothing about what must or must not be the case."Slide19

BUT ACCORDING TO KRIPKE

Kripke

also raised the prospect of 

a posteriori

necessities

 — facts that are necessarily true, though they can be known only through empirical investigation. Examples include

“

Cicero

 is 

Tully

”, “Water is H

2

O” and other identity claims where two names refer to the same object

.

EPISTEMOLOGY CANNOT BE CONFUSED WITH METAPHYSICS!Slide20

FURTHER READINGS:

http://plato.stanford.edu/entries/zombies/#2Slide21