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Mind and Body
Clark Wolf
Department of Philosophy
Iowa State University
[email protected]
Body and Mind:
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.
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.
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.
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.
Considerations Suggesting
Physicalism:

Contemporary Neuroscience assumes
physicalism.

Physical Evidence (Anasthesia, etc)

Mind-Brain Identity and “Split Brain”
cases.
Split Brain
Split Brain
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.
Split Brain
“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.”
Split Brain
Split Brain
Split Brain?
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?”
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)
2)
3)
4)
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.
The patients have two minds (one associated with each
hemisphere), one of which can talk and one of which cannot.
The patients have one mind, involving both hemispheres,
which is not as well integrated as normal minds.
In normal situations, the patients have one normal mind, but
the experiments in question cause this mind to split into two.
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.
Zombies?
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 blackand-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.”
Mary (Frank Jackson)
Is there a further fact about <perceiving the
color red> that would not be known, even by
someone who knew all the physical facts?
If so, does this show that physicalism is not
true?
Case 2: Zombies?
“Consider a zombie. Not the braineating 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?”
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?
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)
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?