Introduction to Philosophy
Lecture 12
Minds and bodies #1 (Descartes)
By David Kelsey
Descartes’ philosophy of mind
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The central Question in the philosophy of mind:
– What is the relationship between your mind and your body?
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Descartes’ philosophy of mind:
– Descartes was a dualist. A dualist:
• Your body is physical and your mind is mental, so they are distinct.
• The Mind as soul…
• Reincarnation and life after death…
• Ghosts, angels, demons, astral projections, etc.
– His brand of Dualism is known as Interactionism.
• The Pineal gland…
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Although Descartes is a Dualist, one could hold on to the view that is known as
Physicalism.
• Physicalism says everything is physical or material substance.
• This means that if there is such a thing as your mind at all, it is a physical object,
presumably your body or part of it.
Descartes’ 1st argument for Dualism
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Descartes was famously a dualist, and his second Meditation contains one of his arguments
for dualism.
1. I can doubt that my body exists.
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His argument for this premise comes in his evil demon argument:
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2. I cannot doubt that my mind exists.
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His argument for this premise comes in his cogito argument.
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“I will suppose…that there is an evil demon, supremely powerful and cunning, who works as hard as he can to
deceive me. I will say that sky, air, earth, color, shape, sound, and other external things are just dreamed illusions
which the demon uses to ensnare my judgment. I will regard myself as not having hands, eyes, flesh, blood, and
senses…”(late in Meditation 1)
“I can’t say I am the collection of organs that we call a human body…for I have supposed that none of these things
exist.“ (mid 2nd meditation)
“…Thinking? It comes down to this. There is thinking, and thought alone cannot be taken away from me. I am, I
exist. That much is certain. For how long? For as long as I think--for it may be that, if I completely stopped
thinking, I would also cease to be…I am therefore not admitting that I am anything at all other than a thinking thing-that is, a mind, soul, understanding, or reason…I know that I am…a thing that thinks.” (mid 2nd meditation)
3. Thus, my mind is not the same thing as my body.
The validity of Descartes argument
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Descartes is appealing to a principle now called Leibniz’s law:
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If x and y are identical, then anything you can truly say about x, you can truly say about
y.
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So If Bob Dylan is the same person as Robert Zimmerman, then whatever I can say
about Dylan, I can say about Zimmerman.
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The physicalist is saying “my mind” and “my body” are like “Dylan” and “Zimmerman”-two names for one and the same thing.
Descartes’ 2nd argument for Dualism
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Late in the 6th Meditation:
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…I will note that mind differs importantly from body in that body is by its nature divisible, while mind is
indivisible. When I think about my mind--or, in other words, about myself insofar as I am a thinking
thing--I can’t distinguish any parts; I understand myself to be a single, unified thing. Although my
whole mind seems united to my whole body, I know that cutting off a foot, arm, or other limb would
not take anything away from my mind. And the abilities to will, sense, understand can’t be called
parts, since it is one and the same mind that wills, senses, and understands. On the other hand,
whenever I think of a physical or extended thing, I can mentally divide it, and I therefore understand
that the object is divisible. This single fact would be enough to teach me that my mind and my body
are distinct…
The formalized argument:
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1.) Body is divisible
2.) Mind is indivisible
3.) If x and y are identical, then anything you can truly say about x, you can truly say
about y.
4.) My mind is not the same thing as my body.
Questions about Descartes 2nd argument
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What about premise 2?
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Premise 1?
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But what about premise 2?
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Is it true that the mind is indivisible?
Descartes 3rd argument for Dualism
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Descartes’ third argument, the real distinction of mind and body:
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1. God can create anything that I can clearly and distinctly conceive--there being no
impossibility in it.
2. If God can create one thing independently of another, the first thing is distinct from
the second.
3. I have a clear and distinct idea of my essence as a thinking thing.
4. So God can create a thinking thing (a soul) independent of a body. (from 1 & 3)
5. I also have a clear and distinct idea of my body as an extended thing--its essence.
6. So God can create a body independently of a soul. (from 1 & 5)
7. So my soul is a reality distinct from my body. (from 4 & 6)
8. So I, as thinking thing (soul), can exist without my body. (from 7)
Understanding the argument for the
real distinction & Descartes criterion
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In Descartes argument for the real distinction, he makes use of his criterion for
truth:
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The Cogito is the basis for Descartes’ criterion. He first introduces the criterion in
Meditation III.
Descartes knows the cogito. He knows it with certainty. He takes this knowledge as a
model by which to judge other beliefs.
1. Descartes is certain that he exists as a thinking thing.
2. Descartes asks himself, What is it about this proposition that accounts for my
certainty that it is true?
3. His answer: the fact that I grasp it so clearly and distinctly that I perceive it could not
possibly be false.
4. He concludes: let this be the criterion: whatever I grasp with like clarity and
distinctness must also be true.
The Criterion: clear and distinct perceptions
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Clear and distinct perceptions:
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So Descartes holds that anything which he perceives clearly and distinctly is true.
The perception must be as clear and distinct as the way in which he perceives the
cogito.
• For a belief to be clear:
– something is clear when it is “present and apparent to an attentive mind, in the same
way as we assert that we see objects clearly when, being present to the regarding eye,
they operate upon it with sufficient strength.” (Principles of Philosophy, 1.45)
– Example:
• For a belief to be distinct:
– Distinct: “so precise and different from all other objects that it contains within itself
nothing but what is clear”.
– It must be impossible to confuse the idea with any other idea
Understanding & Evaluating the argument
for the real distinction of mind and body
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Explanation of the argument:
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1. God can create anything that I can clearly and distinctly conceive--there being no
impossibility in it.
2. If God can create one thing independently of another, the first thing is distinct from
the second.
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3. I have a clear and distinct idea of my essence as a thinking thing.
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Anything that is clearly and distinctly perceived can be made by God to be exactly as it is
perceived.
But if I clearly and distinctly understand one thing apart from another it follows that these things
could really be separated by God and so they are distinct.
Questions:
This follows from what?
4. So God can create a thinking thing (a soul) independent of a body. (from 1 & 3)
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A body-less soul…
Understanding & Evaluating
the end of the argument
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Understanding the end of the argument:
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5. I also have a clear and distinct idea of my body as an extended thing--its essence.
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He perceives clearly and distinctly that body is extended…
6. So God can create a body independently of a soul. (from 1 & 5)
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A soulless body…
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7. So my soul is a reality distinct from my body. (from 4 & 6)
8. So I, as thinking thing (soul), can exist without my body. (from 7)
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Question:
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Must it follow from the conclusion that the soul and body are different substances altogether?
Descartes’ Interactionism
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Descartes’ view:
– So Descartes holds that each of us has a physical part (the body) and a mental part (the soul).
– Descartes was an Interactionist.
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Interactionism: says that minds and bodies causally interact:
– “”…For example, when the nerves in the foot are moved with unusual violence, the motion is
communicated through the middle of the spine to the center of the brain, where it signals the mind to
sense a pain “in the foot.” This urges the mind to view the pain’s cause as harmful to the foot and to
do what it can to remove the cause.” (end of the 6th meditation)
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Minds cause things to happen to bodies.
• When you act, your mind causes your body to move.
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Bodies can cause things to happen to minds.
• When you experience the physical world, your body is relaying your sensations to your mind.
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According to Descartes, the interactions take place in the pineal gland.
Problems for Descartes:
the problem of interaction
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Spooky causation:
– If Interactionism were true, bodies would have to behave in ways that can’t be explained in physical
terms.
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A causal laws…
But human bodies (even pineal glands!) appear to obey those laws just like the rest of the physical
world.
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The mental causing the physical: spooky causation.
So there would have to be exceptions to the causal laws normally governing physical things.
Think about the complex workings of your body…
Possible Dualist response:
– Deny that minds ever cause anything physical to occur.
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This is called Epiphenomenalism…
Problems for Descartes:
the problem of other minds
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The problem of other minds:
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I can’t doubt that I have a mind.
But I can doubt that you have one, just as I can doubt that you have a body.
For all Descartes’ argument shows, I might be the only human being with a mind.
How do I know that I’m not?
This is called the problem of other minds.
Are people just meat machines?
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It seems as though there’s no way to know that other people aren’t just meat machines…
So Descartes Dualism leads to skepticism about other minds.
Final thoughts on Descartes
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Does Descartes solve the problem of the criterion?
– His criterion is this:
• Anything which he perceives clearly and distinctly is true.
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He justifies this criterion in virtue of the fact that his perception of the cogito is
clear and distinct…
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From this criterion he infers:
• if God can create one thing independently of another, the first thing is distinct from
the second and because he has a C&D idea of his essence as a thinking thing
while he has a C&D perception of his body as an extended thing it follows that
mind and body are distinct… (Med. VI)
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But we can still ask: does he really provide sufficient justification for the
criterion?