Lecture NineThe Zombie Argument人皮囊论证

The most famous philosopher who put forward the zombie argument

• avid John Chalmers (born 20 April 1966) is an Australian philosopherspecializing 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.

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).

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.

A Terminological Problem: What is consciousness?• Here consciousness means “qualia”.• Qualia ( /ˈkwɑːliə/ or /ˈkweɪliə/), singular "quale"

(Latin pronunciation: [ˈkwaːle]), 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'.

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.

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.

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.

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).

•

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.

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.

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.

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.

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.

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.)

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’

MORE ON THIS:• Saul Aaron Kripke (born

November 13, 1940) is an American philosopher andlogician. 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 tomathematical logic, philosophy of language, philosophy of mathematics,metaphysics, epistemology, and set theory.

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."

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 H2O” and other identity claims where two names refer to the same object.

• EPISTEMOLOGY CANNOT BE CONFUSED WITH METAPHYSICS!

FURTHER READINGS:• http://plato.stanford.edu/entries/zombies/#2