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Mind and Body Clark Wolf Department of Philosophy Iowa State University

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1 Mind and Body Clark Wolf Department of Philosophy Iowa State University

2 Body and Mind:

3 Dualism and Monism Dualism: Mind and body are different substances that interact but which are essentially different Monism: There is only one “substance” involved in mind/body. Mind and body are not distinct entities.

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5 Monism: ultimate reality is all one kind of thing. Physicalism: Mind and body are both physical entities. Idealism: Mind and body are both mental entities. Neutral Monism: The ultimate ‘stuff’ of reality is neither mental nor physical.

6 DESCARTES: Mind and Body: Descartes is a Dualist: he argues that mind and body are different, separate substances. Here is one Cartesian argument for Dualism: 1) If one substance has a property P while another substance lacks property P, then the two substances are not identical. 2) I can doubt the existence of my body: my body has the property of 'dubitability'. 3) I can't doubt the existence of my mind: my mind lacks the property of dubitability. 4) Therefore my mind is a different substance from my body.

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8 Descartes’s Argument for Dualism: Reservation: is 'dubitability' a property of things or of thinkers? Perhaps premises two and three say more about Descartes thought processes than about the things Descartes is considering.

9 Considerations Suggesting Physicalism: Contemporary Neuroscience assumes physicalism. Physical Evidence (Anasthesia, etc) Mind-Brain Identity and “Split Brain” cases.

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17 Split Brain

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19 KEY RING EXPERIMENT: ‘Key ring’ is flashed on a screen for a tenth of a second so that ‘key’ appears in the left visual field and ‘ring’ in the right. If split-brain subjects are asked to say what they saw, they respond that they saw ‘ring’ and show no sign of seeing ‘key’. But, if they are asked, instead, to retrieve with their left hands the object named on the screen from an array of items concealed from sight, they will pick out a key while rejecting a ring. Asked to point with the left hand to the object named on the screen, they point to a key or a picture of a key and not to a ring or a picture of a ring. If they are allowed to use both hands to pick out the object named from an array of items hidden from sight, their left and right hands work independently, the right settling on a ring while rejecting a key and the left doing the opposite. Someone seems to have seen ‘key’. Someone else seems to have seen ‘ring’. No one seems to have seen ‘key ring’. With suitable controls, input from the other sensory modalities, except taste, can also be confined exclusively to one hemisphere. When a response depends upon it, split-brain patients behave in similar abnormal ways.

20 Split Brain

21 “The standard explanation of such behaviour is roughly as follows. The structure of the visual system assures that the left half of the field of vision is conveyed to the right hemisphere and vice versa. Normally, information about the contralateral visual field is supplied to each hemisphere by neural communication across the commissures and by subsequent eye movement. Since the commissures of split-brain patients are severed and the short exposure time serves as a control for eye movement, their right hemispheres see only the word ‘key’ and their left only the word ‘ring’. In most people, speech production is localized in the left hemisphere; and so the oral response to the question reports only what the left hemisphere saw: the word ‘ring’. The left hand is primarily controlled by the right hemisphere; so it retrieves the object the right hemisphere saw named – a key – and points to a key or a picture of a key. (Notice that this explanation presupposes speech comprehension in the mute right hemisphere.) Similarly, the right hand is primarily controlled by the left hemisphere, thus accounting for the independent search of items concealed from sight. The failure to elicit any response suggesting that ‘key ring’ was seen is that the contents of the visual field available to each hemisphere are not the same and, because of the severing of the commissures and the experimental controls, not communicated to the opposite hemisphere.”

22 Split Brain

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24 Split Brain?

25 Split Brain What do these cases tell us about the relationship between “mind” and “body?” What do these cases tell us about the concept of the “self?”

26 Unified Self? How Many Minds? Four interpretations of the data: As Nagel points out, there seem to be several different interpretations of the data. He distinguishes the following (I collapse his first two interpretations into (1) below): 1) The patients have one mind associated with the left hemisphere; the responses associated with the right hemisphere are not the activities of a mind at all. 2) The patients have two minds (one associated with each hemisphere), one of which can talk and one of which cannot. 3) The patients have one mind, involving both hemispheres, which is not as well integrated as normal minds. 4) In normal situations, the patients have one normal mind, but the experiments in question cause this mind to split into two.

27 Nagel’s View: None of these solutions work. This should lead us to call into question the concept of the “self,” or the “unified self” that plays such a role in Descartes. Next: Zombies and Phenomenal Consciousness.

28 Zombies?

29 Case 1: Mary (Frank Jackson) “Mary, a leading neuroscientist who specializes in color perception. Mary lives at a time in the future when the neuroscience of color is essentially complete, and so she knows all the physical facts about colors and their perception. Mary, however, has been totally color-blind from birth. (Here I deviate from the story’s standard form, in which—for obscure reasons—she’s been living in an entirely black- and-white environment.)” “Fortunately, due to research Mary herself has done, there is an operation that gives her normal vision. When the bandages are removed, Mary looks around the room and sees a bouquet of red roses sent by her husband. At that moment, Mary for the first time experiences the color red and now knows what red looks like. Her experience, it seems clear, has taught her a fact about color that she did not know before. But before this she knew all the physical facts about color. Therefore, there is a fact about color that is not physical. Physical science cannot express all the facts about color.”

30 Mary (Frank Jackson) Is there a further fact about that would not be known, even by someone who knew all the physical facts? If so, does this show that physicalism is not true?

31 Case 2: Zombies? “Consider a zombie. Not the brain- eating undead of movies, but a philosophical zombie, defined as physically identical to you or me but utterly lacking in internal subjective experience. Imagine, for example, that in some alternative universe you have a twin, not just genetically identical but identical in every physical detail—made of all the same sorts of elementary particles arranged in exactly the same way. Isn’t it logically possible that this twin has no experiences?”

32 Zombies Are zombies conceivable? If they are conceivable, does this show that they are possible? If they are possible, does this show that there is more to consciousness than the physical facts?

33 P1. I can conceive of zombies (or a zombie world), i.e., creatures that are physically identical to conscious beings but entirely lack consciousness (a world physically identical to ours but entirely devoid of consciousness). P2. If zombies (or a zombie world) are conceivable, then they (it) are metaphysically possible. C1. Zombies (or a zombie world) are metaphysically possible. (P1, P2) P3. If zombies (or a zombie world) are metaphysically possible, then facts about consciousness are facts over and above the physical facts. C2. Facts about consciousness are facts over and above physical facts. (C1, P3) P4. If physicalism is true, then there are no facts (about consciousness) over and above the physical facts. C3. Physicalism is false. (C2, P4)

34 Case 3: Aristotle’s Brain Suppose I knew all of the physical facts to be known about Aristotle’s brain state, at the time when he was writing Book V of the Nichomachean Ethics. Would I then know everything there is to be known about Aristotle’s conscious state at that moment? Or might I still fail to know what it was like to be Aristotle?

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