We're going to look
at two questions
in the philosophy of mind.
The first question that we're
going to deal with today
concerns the relationship
of the mind to the body.
The second question,
which we're going
to turn to in
another week or two,
concerns personal identity.
What is it about
us that makes us
think that there is a person
that remains throughout time?
In other words, what makes
one and the same person
exist throughout time?
And both of those
questions deal essentially
with trying to get
a handle on, what
is the nature of a human being?
I mean, what are we essentially?
What are we at our essence?
What is our very nature?
And so all of these
topics in metaphysics
are kind of the mind
blowing kind of questions
that you think about when you
think about doing philosophy,
but they're deeply important,
because without them, you
really don't understand
what a human being is.
And if you think about what the
main goals of philosophy are,
one of them should
obviously be just
understanding human
beings, understanding
the nature of human beings.
And so we're going to look at
the philosophy of mind today.
And particularly, we're going
to look at Cartesian dualism.
And Descartes was a
proponent of the view
that there are two kinds
of things in the world.
There are mental things and
there are physical things.
And he believed that those two
things interacted in a way.
And that's what
a human being is.
A human being is an
interaction of mental substance
and physical substance.
So that's the
first main question
that we're going to talk
about during this unit,
is about the relationship
of the mind and the body.
So here is Rene Descartes.
He was around late
1500s, early 1600s
and he's considered the
father of modern philosophy.
He comes around right
after the Renaissance.
And a lot of things
had sort of blown up
during the Renaissance,
as you guys know.
Advances in science,
as well as developments
in religion and in
art, and Descartes
was, of course, enthralled
with all of these changes.
And what he wanted
to do is develop
a kind of philosophical
method that
would use the same kind
of rigor and discipline
that you find in
the hard sciences,
in something like a geometry.
And he wanted to use
that same kind of rigor
and apply it to
philosophical questions.
Descartes, of course, is
also famous in algebra.
So you've probably
already learned
about Descartes in
your math classes.
And today, we're going
to look specifically
at some of the things he
had to say philosophically.
So looking at the
developments that he
had seen in science, where
Copernicus gives rise
to Kepler and then Galileo,
they were all figuring out
the mechanics of the
stars and the planets
and how all that stuff worked.
Harvey was figuring out the
circulation of the blood.
Gilbert was figuring out
things about magnetism,
which then gives rise
to Newtonian physics.
In religion, you've
got Luther and Calvin
making these dramatic kind
of developments and sort
of rebelling against
the Catholic church.
In art, you've got Leonardo da
Vinci doing his wonderful work.
And in particular, Descartes
was impressed with the certainty
and precision of mathematics.
And in fact, he invented
coordinate geometry.
And what he wanted to do
is bring that same kind
of certainty and precision
that you find in mathematics
and bring that to bear
in philosophical kind
of questions.
So he comes up with this
method of philosophy
that seeks ultimate certainty.
And he says to never
accept anything
except clear and distinct ideas.
He says that when
faced with a problem,
divide it into its
constituent parts
and attack it sort
of part by part.
Order your thoughts
from simple to complex.
And in doing this process,
always check thoroughly
for oversights.
And he thought that by sort of
employing this method that you
could achieve some kind
of absolute certainty,
even in these very kind
of difficult philosophical
questions.
So what we're going
to look at today
is Descartes' approach
to the mind body problem.
And Descartes advocates
a type of dualism.
And this type of dualism
then was advocated so well
by Descartes that they
named it after him.
So Cartesian is the adjective
form of the name Descartes.
So Cartesian dualism is a
particular approach to the mind
body problem which says this--
that ultimately the
universe is composed
of two different substances.
There are mental substances and
there are physical substances.
The essence of a
mental substance
is thinking, or consciousness.
And the essence of a physical
substance is extension.
And that's just a fancy word
that means basically volume.
And so Descartes says
that the universe is
composed of two kinds of stuff.
There's mental stuff and then
there's physical stuff, right?
And the physical
stuff is what we're
sort of familiar with
in our day to day lives.
Trees and water and rocks
and buildings and bricks
and chairs and tables
and walls and roofs
and bicycles and cars--
all that stuff is
made out of stuff.
You can grab it, you can
touch it, you can see it,
you can smash it together.
But mental stuff
is not like that.
Mental stuff is the
stuff of thought.
It's the stuff of consciousness.
And that stuff you can't sort
of grab, you can't hold onto,
but it's stuff nonetheless.
So it's a kind of
immaterial stuff.
So Descartes thought
that there was
material stuff,
or physical stuff,
and there's mental stuff,
or immaterial stuff.
And he believes that these two
kinds of stuff work together.
They interact with each other.
So Cartesian dualism is
also called interactionism,
because he believes that minds
and bodies work together, they
interact with each other.
They're causally
linked, so that things
that happen mentally cause
things to happen physically.
And things that
happen physically also
cause things to happen mentally.
Now, dualism is not the only
way to approach the mind body
problem.
Another way to approach
it is to be a monist.
Monists believe there's only one
kind of stuff in the universe.
And we will look at some
versions of monism later on.
So today, we're going to
look at the view of dualism,
that there's two kinds
of stuff, mental stuff
and physical stuff.
So most people walking around,
whether they know it or not,
are some kind of dualists.
And typically, they will
be Cartesian dualists.
So implicitly, people tend to
hold the view that Descartes
held, they just
don't really realize
that their common sense
view of the universe
comes from Descartes.
So what are some
of the reasons why
people tend to be Cartesian?
The first thing about
Cartesian dualism
that makes it so plausible
is that it kind of fits well
with these obvious
philosophical facts.
First obvious philosophical
fact is that you have a mind.
Another philosophical fact
is that you have a body.
And a third philosophical
fact is that minds and bodies
work together.
But furthermore, it seems
like minds and bodies
aren't the same kind
of thing, that minds
have a kind of
qualitative content,
that when I have a
mental experience, when
I bite into a lemon and I
have that immediate kind
of sour taste, it seems sort
of obvious that that sourness
can't simply be
a matter of, say,
neurons firing in my brain.
It can't simply be a matter
of a kind of physical process.
So we know that there is a
physical process that goes
on when I bite into a lemon.
There are nerve
endings that are firing
that makes the muscles
in my jaw contract, which
makes my jaw bite down.
And there are sort of chemical
reactions going on in my tongue
and those reactions are
sending signals to my brain.
And we know all of that.
But there's also a kind of
quality to the experience that
doesn't seem to be
reducible to just the kind
of physical phenomenon, right?
So there is a qualitative
feel of experiences,
a distinctive taste of apples
and pineapples and lemons.
There is a distinctive kind
of agony of a headache.
And those things don't seem to
simply be physical phenomena.
They seem to be something
else, mental phenomena.
Another thing is that
our mental states tend
to have intentional content.
They seem to be about
objects and states of affair.
In other words,
they kind of latch
on to things in the world.
And that seems only possible
with a kind of immaterial mind.
The next thing
that we'll mention
about sort of obviousness
of Cartesian dualism
is that we have a kind
of privileged access
to the contents of our
own mind, that there
are kind of private episodes
that go on in our mind,
whereas events that go on in
our body, at least in principle,
are publicly observable.
So if you cut me open, you can
look at the chemical reactions
that are going on on my tongue.
You can look at the
electrical impulses
that are going on in my
muscle fibers or whatever.
But you can't sort look at
what's going on in my mind
simply by cutting open my
brain and looking at that.
So if we have a group of people
sitting in a room and we say,
OK, look around.
How many chairs are in the room?
Each one of us in the room is
in a kind of equal position
to say with accuracy how
many chairs are in the room.
We all look around and
we say, 1, 2, 3, 4, 5.
OK, there are five
chairs in the room.
And we all say, there are five.
However, if I say, is Betty
experiencing a headache
right now?
There's really only one person
in the room who really knows
the answer to that question--
Betty herself.
And I can look at that and
I can see that maybe she's
rubbing her head
or maybe there's
a tear forming in her eye
or she's taking medicine.
And I may say, oh,
it looks like Betty
must be experiencing a headache,
because after all, she's
taking aspirin.
But I don't really know whether
Betty is experiencing headache.
Only she really knows whether
she's experiencing a headache.
And so it seems like the
mind must be something
else than simply the body.
And furthermore, related to this
privileged access, this privacy
that we have to the
contents of our own mind,
it seems like we can't
be wrong about it, right?
And so that's called
incorrigibility.
We can't be wrong.
So if I feel a
pain, I feel a pain.
And that's just the
fact of the matter.
You never experience
anything like oh, that hurts,
that hurts so bad.
Oh, wait, no, it doesn't.
I was mistaken, right?
Believing you are in pain
is what it is to be in pain.
Experiencing pain is
experiencing pain.
And you can't be wrong about it.
Now, you can be wrong about how
bad something is going to hurt.
This happens to me all the
time when I go to the doctor.
I'm very afraid
of getting a shot.
I'm afraid of needles.
And so I always anticipate it
hurting really, really badly.
And then it happens and
then it's not that bad,
and I say, oh, wow,
it wasn't as bad as I
thought it was going to be.
You can be wrong about
things like that.
But if you feel a
pain, you feel a pain.
And that just is what
it is, to feel a pain.
You can't really be wrong about
the contents of your mind.
You could see a pink elephant.
And maybe that pink
elephant is really there.
Maybe it's not really there.
But seeming to see a pink
elephant is what it is.
So you would never
say, it seemed to me
that I was seeing
a pink elephant.
And maybe I wasn't
seeing a pink elephant,
but it didn't even
really seem to me
that I was seeing
a pink elephant.
In other words, if it seems that
you're seeing a pink elephant,
then you are experiencing
a pink elephant.
End of story.
You can't be wrong about that.
The next thing that
seems to be obvious
is that there is a kind
of causal relationship
between the mind and
the body, that when
I step on a sharp tack,
something happens in the body
obviously.
The skin breaks.
The nerve endings fire.
But also something happens
in my mind, an ouchiness,
a painful experience.
And then that painful experience
then causes other things
to happen in my body,
namely I shout out,
ouch, that hurts, or I
start cussing or whatever,
and I hop around the room.
And then lastly, there seems to
be a kind of unity to our mind.
The things that happen
in our conscious mind
are all kind of unified.
So if you have an
experience, let's say,
of going to a concert and
you're watching the concert
and you're listening to
the music at the same time,
those experiences all
seem to be sort of unified
in a single place--
namely, in your conscious mind.
And that doesn't seem
possible unless there
is this sort of extra
dimension to human beings
besides the merely
physical thing.
So because dualism seemed
sort of obvious to many people
around the world, we can
trace back this view at least
to Plato.
But of course, I
don't think even Plato
invented the idea of dualism.
Dualism seems to be a kind of
very natural, default position
for all people around the
globe throughout history.
We saw an article
in our last unit
called the ghosts we think we
see, or something like that.
And that was about how
natural it is for human beings
to kind of apply
agency to phenomena
when they experience them.
And of course, Plato
realized that, too.
And Plato, of course,
was deeply influential
in Western civilization.
So it's not surprising that
most of us walking around
in the Western
world are dualists.
Plato had a different
kind of version of dualism
than Descartes.
And we can read about
Plato a little bit more
in our [INAUDIBLE] textbook,
but the short kind of story
is that Plato believed in this
theory of the forms, which
is this kind of
world of perfection.
And we can kind of tap into
that world with our minds.
And that's not something
that just our body can do,
but that we need a
kind of immaterial mind
to tap into that.
And then lastly, the
possibility of Cartesian dualism
is really reinforced, then,
with our typical Judeo-Christian
worldview, the worldview that
says that what I am essentially
is an immaterial soul.
The soul is me.
The soul kind of
houses my essence,
it houses my personality.
And the soul is the
thing that continues
to live when my body
disintegrates, right?
When my body dies,
I don't really
die, as long as my soul
continues to go on.
And it's a kind of
immaterial thing
that can float up to heaven,
and it really exists,
and it's a different kind
of sphere of existence
and it's not matter.
It's not stuff.
But nevertheless, my
mind kind of continues
to live up there in
heaven as long as I
am a good little boy and
all that kind of stuff,
I get to go to heaven.
And so the idea that I have this
kind of dual aspect to myself,
I have my physical stuff
that kind of houses my soul
when my body is alive, but
that essentially my soul
is what I really am,
and that that part of me
can flow away later.
That seems to fit
very well, sort of
obviously with the
Judeo-Christian worldview.
And so whether or
not you're explicitly
kind of a proponent of the
Judeo-Christian worldview,
most all of us basically
are the descendants
of Greek philosophers like
Plato, Aristotle, and Socrates.
And so because
they were dualists,
it seems very
natural also for us
to be dualists, just
because we grew up
in the Western civilization.
Of course, it's not just in the
West that people are dualists.
There is, of course, another
sort of type of dualism
that's common in
the east as well.
And you can learn more about
that if you take, for instance,
eastern philosophy, which
is offered every spring
semester at MCC.
So most people
walking around are
dualists because it just
sort of fits very well
with these obvious
philosophical facts
about how the mind
and body just clearly
have to be different
kinds of things,
but also clearly they have
to work together somehow.
OK.
Well, Descartes, as
a good philosopher,
didn't just assert dualism.
Of course, he
argued for dualism.
He didn't just take it
to be commonsensical.
He said, well, if I
want to be a dualist,
I have to convince myself
that I should be a dualist.
I have to convince
you to be a dualist.
And so I'm going to
advance arguments
in favor of my brand of
dualism, Cartesian dualism.
And the two arguments that
we're going to look at today
are called first the doubt
argument and secondly
the divisibility argument.
Descartes has these
other arguments
that you can kind of find,
but the doubt argument
and the divisibility
argument are probably
his two best arguments and his
two most well-known arguments.
And so we're going to see those
arguments today and critically
assess them and
see whether or not
we think they ultimately work.
We're going to start
with the doubt argument.
And just by way
of preliminaries,
we've all heard
the famous quote,
"I think, therefore I am."
Some people don't realize that
that comes from Descartes.
Yep, he was the
author of that quote.
And secondly, most
people don't quite
realize what he meant by that.
So I'll spend a little bit
of time just explaining
that quote, because it fits
into the doubt argument.
Descartes, when he
started doing philosophy,
he wanted to come up with this
sort of epistemological method
of certainty.
Epistemology is the
branch of philosophy
that deals with knowledge.
And so he said he wanted
to come up with a method
to establish certainty.
And he looked around at all
the things that he was taught
growing up, and all the things
that he believed, and he said,
you know what?
A lot of things that I
was taught to believe
ended up to be wrong.
And so I'm sure that I must
have some beliefs in my mind
that are false.
Of course, the problem
is, which ones, right?
I mean, if you
believe something,
by definition you believe
it to be true, right?
So there's a kind of paradox
where everyone kind of has
to admit to
themselves that there
are some things that they
believe that are probably
false.
Except identifying
something that you believe
that is false is impossible,
because if you already believed
that it was false,
well, then, you
wouldn't believe
it anymore, right?
So he says, well,
geez, I don't really
know how to examine all my
beliefs one by one by one
and see which one of
these is probably false,
so what I'm going to do is
throw them all out, right?
So I'm going to start
with universal doubt.
I'm going to doubt everything.
I'm going to doubt even the
most sort of obvious things.
Well, where does that leave me?
Well, Descartes says,
there's one thing
that I'm not able to doubt--
namely, that there is
doubting going on, right?
So Descartes pictures
himself, sitting at his desk.
And he says, well, here I am.
I'm writing this
philosophical essay
and I'm sitting at this desk
and I have some wax in my hand
and a pen in my hand and there's
paper sitting in front of me.
And it seems sort of obvious
that here I am at my desk,
but after all,
maybe I'm dreaming.
I've had experiences in my life
where I think I'm at my desk
and I think I have
paper in front of me
and I think I'm thinking
about some philosophical kind
of problem and then, lo
and behold, I wake up,
and there I am in bed
and the whole thing
was sort of a dream.
And then I say, oh, well,
OK, that was just a dream.
I wasn't really at my desk.
I was just tricked into
thinking that I was at my desk.
So what Descartes did hundreds
of years before the fact is he
came up with the matrix idea.
In the matrix, as you
guys know, everybody
exists in this sort
of pod and everyone
is hooked up to this
computer, and the computer
generates all of
these experiences that
aren't really real.
And Descartes says,
yeah, maybe we're
all just hooked up to some
computer program that's
making us experience
lots of things,
but it's not really real.
Now, of course, Descartes
didn't know about computers,
but he had this idea
of a kind of evil demon
that played the same role as
the computer in the matrix,
where the evil demon basically
puts us under a spell
and so that all of our
conscious experiences
are a kind of trick.
And Descartes goes one step
further than the matrix--
because in the matrix,
at least, our bodies
are in these pods that are
then hooked up to the computer.
And Descartes says, well,
maybe I don't even have a body.
I mean, here I am, and
I'm looking at my hands
and my hands are in
front of me, but maybe
that's part of the dream, too.
And so he says, well, there's
one thing that I cannot doubt.
I mean, even if I'm being
tricked by this evil demon,
I can't doubt that there is
some doubting going on, right?
So I don't know whether
the desk exists.
I don't know whether
the paper exists.
I don't whether the pen exists.
I don't know if my hand exists.
But I know that I exist,
because here I am thinking.
I'm thinking to myself,
hey, maybe my pen
doesn't really exist.
Well, that proves
to me immediately
that there is at least
something there that's thinking.
So as a thinking
thing, I must exist.
So insofar as I doubt,
there is doubting going on.
Insofar as there is
doubting going on,
there is a type of
thinking going on.
And so insofar as
that, then there
is some conscious
being that is there.
And so Descartes says,
"Cogito Ergo Sum," which
is just a fancy Latin
way of saying, "I think,
therefore I am."
So the one thing that
Descartes establishes
with absolute certainty
from the very beginning
is that he, a thinking thing,
must exist as a thinking thing.
And then from there, you can go
and read more about Descartes.
But that's just his first step.
And then he goes on to prove
that God exists and then he
goes on to prove that
external objects exist
and mathematical objects
and blah, blah, blah.
So the story
continues from there,
but he starts with the idea
that he, as a thinking thing,
exists.
So that's the first
kind of preliminary
of the doubt argument.
The second preliminary
of the doubt argument
refers to something that's
called Leibniz's law.
Leibniz was another
philosopher who actually
came after Descartes, but
he developed this idea
that actually was already kind
of implicit in what Descartes
was saying.
And Leibniz's law has two parts.
The first part is
called the principle
of the indestructibility
of identicals.
And the principle of the
indiscernability of identicals
goes like this--
if two things are
identical, namely if they're
one and the same,
numerically one and the same,
then they have exactly
the same properties, OK?
So if I bring my calculator
to class on Monday
and then I bring a calculator
to class on Wednesday,
and you are asking
yourself, does
[INAUDIBLE] have
two calculators,
and he brought one
of them on Monday
and he brought another
one of them on Wednesday?
Or does he have
only one calculator,
And he brought it, the one
and the same calculator,
with him on Monday, he
brought it again on Wednesday?
You would say, well,
how would I know that?
Well, if it's the same
calculator on both days,
then it has exactly
the same properties.
There's another side
to Leibniz's law, which
is called the principle of the
identity of indiscernables,
which says if two things have
exactly the same properties,
then they are identical.
Now, the second part
of Leibniz's law
is more kind of controversial.
Not everyone agrees with the
second part of Leibniz's law.
But that's OK, because Descartes
only needs the first part,
all right?
So Descartes is going to use the
first principle, the principle
of the indiscernability
of identicals
to make his argument work.
OK, so now let's look
at the argument proper.
The doubt argument--
premise one says, I
can doubt that my body exists.
OK, so remember that
Cogito Ergo Sum point
that Descartes made previously.
He says, look, I don't
know whether I really
am sitting at a table.
I don't know if there
really is a table.
But for all that, I don't
even know that my hands exist,
that my arms exist, that my
legs exist, that my body exists.
I mean, I might just be a mind.
You can at least doubt
that your body exists.
So in other words,
take the matrix example
and go one step further.
So we're not just bodies in
pods hooked up to a computer.
We're just nothing at all.
I mean, there's just no
physical thing at all.
And yet, your mind
is still there.
You can at least doubt
that your body exists.
On the other hand, the second
point of the Cogito Ergo Sum
argument says, but I cannot
doubt that my mind exists once
I say to myself, I doubt that
blah, blah, blah, well, then,
there is doubting there.
If there is doubting there
is consciousness there.
If there is consciousness there,
then there is a mind there.
There is thinking going on.
So as a thinking thing,
you cannot doubt your own
existence.
But you can doubt
your bodily existence.
So maybe what the demon
has tricked us about
is that we have a body.
Maybe we really
don't have a body.
And so then we use
that first principle
from Leibniz, the
indiscernability of identicals,
for the third premise.
And it says, well, OK, if
two things are identical,
then they have exactly
the same properties, OK?
So what Descartes
is saying is, OK,
let's ask ourself whether
or not my mind could simply
be my body.
I mean, in other words,
is my mind simply
my brain, all right?
And he says, no.
My mind has to be something
other than my brain,
because I can doubt
that my body exists.
In other words, I can
doubt that my brain exists.
But I can't doubt
that my mind exists.
And so there are two
different properties, right?
My mind is not doubtable,
but my body or my brain
is doubtable, right?
So therefore, the
conclusion that follows,
from one, two, and three--
I, a thinking thing, cannot
be identical with my body.
In other words, my mind can't
simply be a bit of my body.
I mean, the best candidate,
as we know, for today,
would be the brain.
And Descartes says, no, I
can't be simply a brain.
I have to be something
over and above that,
because I can doubt
that my brain exists,
but I cannot doubt
that my mind exists.
And if my mind
just were my brain,
they would have exactly the
same properties, but they don't.
OK, that's the argument,
the doubt argument.
Let's then turn to
some criticisms.
Both of these criticisms kind
of attack that third premise--
namely, Leibniz's
principle there,
about how if two things
are identical, then
they must have the
same properties.
The Oedipus example
goes like this.
Well, we all know
the story of Oedipus.
Well, if you don't
know it, you should
take a class in Greek tragedy.
And the classic Greek
tragedy Oedipus, Oedipus Rex,
goes like this.
Very famous story.
When Oedipus was born,
he was born a prince.
He was born to a king.
And then there
was an oracle that
said that this son will
take over the kingdom
and kill the king.
And the king says, oh, my
god, I can't have any of this.
And he believed the oracle
and he sent Oedipus off
and footed him down a river
or something like this.
I don't remember the
details of the story.
And then, of course, Oedipus,
through fate, of course,
comes back later as a grown up.
And he stumbles
upon the kingdom.
And he meets somebody
named Jocasta.
He falls in love with Jocasta.
And he marries her.
And he kills Jocasta's husband.
And he takes over the kingdom
and he becomes throne.
And lo and behold, what
he doesn't know all along
is that Jocasta is his mother.
Oh, my god.
And so then he plucks out his
eyeballs and commits suicide.
And it sounds like Greek
tragedies always end.
Well, they end in tragedy.
So OK, the point is not to
review the Oedipus Rex story,
but to just make a point about
Leibniz's principle, right?
So if you take
Jocasta and you say,
Jocasta is identical to
Oedipus's mom, right?
Oedipus's mom is Jocasta.
They're one and the
same person, right?
So because they're one
and the same people,
they must have the
same properties.
Except Jocasta seems to have
a property that Oedipus's mom
does not have--
namely, that Oedipus
desires Jocasta.
He desires to marry Jocasta,
but if you asked Oedipus,
do you desire to marry your mom?
He'll say, no, I don't.
Of course not.
Of course I don't
desire to marry my mom.
And yet nevertheless,
Jocasta is Oedipus's mom.
And so I think what this
shows us is that just look
at it from a different way.
One and the same
thing can sort of
seem to have
different properties,
but that doesn't mean
that there really
are two things that
you're looking at, right?
And so the example then to apply
it to the mind body problem
would say, well, it
seems like your mind has
certain properties, and it seems
like your body or your brain
has certain properties,
but that doesn't thereby
show that your
mind and your body
must be two different things.
Maybe you just don't realize
that there one and the same.
The second example,
the second sort
of counterexample to the
doubt argument goes like this.
OK, hold up your hand.
Hold up your hand
and now make a fist.
Examine the fist
compared to the hand.
There are some things that you
can say about the fist that
are not true about the hand.
The first has some properties
that the hand doesn't have.
Let's say, for
example, the fist is
good for pounding on the table.
The hand is not good for
pounding on the table.
The fist is good for
punching someone in the nose.
The hand is not good for
punching someone in the nose.
The fist is tight.
The hand is malleable, right?
And so the hand and the
fist have different sets
of qualities.
They have different properties.
But does that show us
that the fist must be
something else than the hand?
No, the fist just is the hand
in a certain configuration.
In other words, the fist could
not exist without the hand.
The hand, of course, could
exist without the fist.
I mean, you could have a
hand and never ball it up
into a tight fist, but
you couldn't have a fist
without a hand.
And if we apply this back to
the mind body problem, you say,
maybe the mind just is the brain
in a certain configuration.
In other words, when the
brain is doing something
in particular, when it's doing
some kind of special activity,
then a mind exists.
You can have a brain, of
course, without a mind.
For instance, if you have a dead
body and you take the brain out
and you plop it down on the
table, there's a brain there.
But plausibly,
there's no mind there,
because the brain is
not doing brain stuff.
It's not doing brain functions.
It's just a blob of
goo at this point.
But, so says the
counterexample, you
couldn't have a mind
without a brain,
just like you couldn't
have a fist without a hand.
And so that seems to show
us that first principle
from Leibniz, the
indiscernability of identicals,
seems to be wrong, that the
first has some properties,
the hand has other properties,
but that doesn't thereby
show that the hand and fist
must be two separate things.
The fish just is the
hand, but when the hand is
doing something in particular.
OK, now, we're going to turn
to the divisibility argument,
which is the second argument
for Cartesian dualism.
And it's arranged as a
standard categorical syllogism.
So that's kind of a special type
of argument that we'll look at.
And it goes like this.
Premise one, all extended
things are divisible.
Premise two, no
minds are divisible,
so therefore conclusion, no
minds are extended thing.
OK, let's take a look
at this step by step.
The first premise is all
extended themes are divisible.
Now, remember.
Extended things just
Descates' fancy way
of saying physical things.
So if you take
anything that you can
find in the physical world,
at least in principle,
you can break it up, right?
So if you take a rock,
you can pound on it
until it breaks into two, and
then you've got two rocks.
You can pound on each
one of those parts
and then you can break
them into four rocks.
And then you can just
sort of keep pounding
into smaller and
smaller bits of dust
until you get down to the
molecular level or something--
I mean, Descartes wouldn't have
understood molecules the way
that we understand them today,
but at least in principle, you
can keep breaking
everything down
into smaller and smaller bits.
The second premise says, yeah,
but minds aren't like that.
You can't take a perception
and cut it in half
and have half of a perception
on one side of the room
and half of a perception
on another side of a room.
You can't take a thought
and cut the thought in half
and throw half the thought
away and save the other half
of the thought, right?
You can't take an
intention and break it up
into half or quarters or 16ths.
Minds just don't work like that.
They're just not divisible.
So anything that you find in
the physical world, at least
in principle, is divisible.
But no minds are invisible.
So that shows us that no
minds are extended things.
Now, as I mentioned,
this argument
is a categorical argument.
It's a standard
categorical syllogism.
And because it takes
the standard form,
it even has a name, the
name of any argument that
takes this same shape
is called an AEE2.
That's just a kind
of label that we
put on these arguments
of this type.
If you want to learn more
about argumentative structure,
you should take philosophy 155,
which is logic and reasoning.
And so for the next couple
minutes, kind of bear with me.
If you haven't taken logic,
I'm going to give you a crash--
very crash-- very quick
course on the diagrams.
And if you have
taken logic, this
will be a really
refreshing review
for you and you'll say, yes,
I understand all this stuff,
because I had it
in my logic class.
So Venn diagrams go like this.
Here's the
divisibility argument.
We can use these circles
to represent the three
categories of things that we're
talking about in the argument.
We've got divisible things.
We've got minds and we've
got extended things.
And each one of
those categories,
at least potentially,
overlaps with one
of the other categories, or both
of the other categories, right?
So in the very middle
of the Venn diagram,
you have the set of all the
things that are divisible
and minds and extended things.
And then, of course,
you've got the overlap
of things that are just
divisible and extended,
and then on the sort of
outer area of each circle,
you've got just, say,
the extended things that
are not mind and
are not divisible,
or just the indivisible
things that are not
minds and not extended things,
just the minds that are not
divisible, not extended.
And so what we can do is
we can take each premise
and we can diagram it
on our Venn diagram,
and then see whether
or not we can read
the conclusion of our diagram.
If we can reach the
conclusion off of our diagram,
it shows us that the
argument is valid.
And if you can't read the
conclusion off of our diagram,
it shows that the argument
is invalid, right?
So not all categorical
syllogisms are valid.
The trick of logic, the
trick of this Venn diagram
is to try to discern whether
or not the argument is valid.
And so here is how it works.
The first premise says
all extended things are
divisible things, so what we do
is we take that extended things
circle and we say, OK,
of all the extended
things in the universe, they
all exist within this circle.
And we're going to block out
the outer edge of the extended
things.
So we're going to say it's
impossible for something
to be extended and not
be divisible, right?
And so we blocked off that area.
So all extended things,
then, are sort of
pushed into the divisible
things category.
And that's exactly what
the first premise says.
It says, of all the
extended things, all of them
are within the category
of divisible things.
The second premise-- so we leave
the first premise diagrammed.
And then we move onto
the second premise.
And the second premise says,
no minds are divisible.
So now, we've added a second
shading and the second shading,
then, crosses out that overlap.
Any area that overlaps the
divisible things and the minds
gets crossed out.
We say, well, there
can't be any minds that
are within the
category of divisible,
so we block that out, right?
So when we block it out,
it means there ain't
nothing in there, all right?
And then that's our diagram.
In other words, this is a
kind of visual depiction
of the information that's
contained in the first premise
and in the second premise.
Now, if that information
is sufficient for us
to read the conclusion,
then the argument works.
It's at least valid.
So the conclusion says,
no minds are extended.
And does the diagram show us
that no minds are extended?
Well, you can see
that the overlap
between minds and extended
is completely crossed out.
We crossed out some of
it in our first premise.
We crossed out more of
it in the second premise.
And there's no more
overlap, right?
So anything that's the
mind has to exist outside--
it has to exist in that sort of
outer area of the mind circle,
outside of the
extended things circle.
That shows us that
the argument is valid.
However, that doesn't
show us necessarily
that the argument is sound.
So one thing that we want
to distinguish in philosophy
are arguments that are
sound from arguments
that are merely valid, so this
argument is at least valid,
but that doesn't mean that we
have to accept the conclusion,
because maybe the
premises aren't true.
And if the premises aren't
true, then the conclusion
is not necessarily true.
So are there reasons to believe
that the premises aren't true?
Yes, there are.
So the criticisms of the
divisibility argument
focus on that second premise,
that no minds are divisible.
And there are two examples
that we'll give you
that seem to suggest
that minds maybe
are divisible in a certain way.
If you've taken intro to
psychology, even in high school
if you took a kind of
intro psychology class,
you probably heard about the
famous story of Phineas Gage.
Phineas Gage lived
in the mid-1800s
and worked on the railroads.
And there was a famous
accident, right?
Which made Phineas talked
about in psychology classes
to this very day.
The accident happened like this.
He's pounding this
railroad spike,
and then there's some
explosion, because, of course,
railroad workers
have to dynamite
their way through
mountains and make tunnels
and all this kind of business.
And so a railroad
spike comes rocketing
through Phineas Gage's head.
It hits his jaw and
continues up through his head
and flies out the top
of his skull, right?
So he's got this
tunnel that's made
through his entire
frigging head, right?
And miraculously, he survives.
The doctor comes up and takes a
look at him and sticks his hand
and sticks his
finger in one hole
and sticks his finger in the
other hole, and lo and behold,
his fingers touch.
And no one can believe that
Phineas survived this accident.
And he seems to be fine.
But then as time
goes on, then Phineas
sort of really changes
in his personality.
He becomes very aggressive,
and his personality changes.
And he becomes very rude
to people and people
said that he's sort of not
the same person anymore.
And at any rate, the
details of the story
are really not important.
And here's a picture
of Phineas' skull,
preserved for all of history.
You can see the hole in
the top of his head there.
The details, of course,
are not really important.
What's important is
the philosophical point
that the story
seems to make, which
is that it seems
that if you, say,
drill a hole in your brain,
then not surprisingly,
you do perhaps drill
a hole in your mind,
that there are bits of your
mind that are literally
cut out if there are
bits of your brain
that are cut out, right?
And if you start
scooping out brain,
then you do scoop out
things like memories.
You scoop out things
like perceptions.
And it seems to show that, well,
the mind is maybe divisible,
that you really can have a
mind without an intact brain.
The second example deals
with the corpus callosum.
The corpus callosum
is this bundle
of fibers, this bundle of
nerves that connects the two
hemispheres of your brain.
So as you guys know, the
brain has kind of two halves.
And the two halves each sort
of do their own kind of thing.
The left brain controls
the right hemisphere
of your body and vice versa.
And you know that if
somebody is left handed,
it means that their
right brain typically
is slightly more dominant.
And if somebody is right
handed, then their left brain
is slightly more dominant.
So you know this already, OK?
Well, the corpus callosum
is is this bundle that
connects the two hemispheres
and it keeps the two hemispheres
in communication.
Well, there is this
surgery that is
done to people who are suffering
from severe epileptic seizures.
And one way that
you can cure them
of severe epileptic seizures
is to cut the corpus callosum.
And so that surgery is called
the corpus callosotomy.
It's just the severing
of that bundle of nerves.
So basically, you cut the two
halves of the brain in half.
And when you do this
surgery, people recover fine
and they act totally normally.
And they go about their day,
totally like everybody else
does, except in these
very controlled kind
of experimental
conditions, you can
get some very weird
results, results
that seem to suggest
that there really
are two minds now that exist
in one person's head, right?
That when you cut
the brain in half,
it's like you cut one mind
and make it two minds.
And so instead of
telling you about this,
I'll just show you a video.
So I've got a link
that I'll post,
so check it out right
after this lecture is over.
Go and check out the link.
And you can see one of
these split brain patients
and you can see how he's acting.
And at any rate, the point that
the criticism is trying to make
is that maybe minds are
divisible after all.
And if that's the
case, of course,
the argument falls down, because
the second premise is not true,
so then the conclusion
is not necessarily true.
OK, so we've seen two arguments
for Cartesian dualism.
We've also seen how just
Cartesian dualism just sort
of seems right.
It just sort of seems obvious.
It just seems that there has
to be something right about it,
just kind of commonsensically.
But now we're going to
look at some criticisms
against the theory--
not just specifically against
the arguments for the theory,
right?
Because we could have
sort of left it at that.
We could have said the
doubt argument doesn't work
and the divisibility
argument doesn't work,
so therefore Cartesian
dualism doesn't work.
But these criticisms that
would go the next step
and say, well,
there are positive
reasons to argue against
Cartesian dualism.
And, of course, there is
a kind of variety of them.
And so we've got six
arguments here to look at.
The first argument
against Cartesian dualism
is really the most potent.
It's the most important.
It's kind of the single biggest
problem of Cartesian dualism.
And that's simply that Cartesian
dualism never really explains
how two radically different
substances could ever
causally interact.
It just remains paradoxically
mysterious, right?
I mean, if the
mind is one thing,
if the mind is immaterial,
and the body is quite
another thing, if the body is
physical, if it's material,
if it's made out of
stuff, it seems impossible
that the mind stuff and the
body stuff could ever really
interact.
And if they did
interact, it seems
that it would have to violate
the law of conservation
of energy or the law of
conservation of momentum.
And we don't see that.
We don't see the
law of conservation
of energy ever being violated.
So it seems that
there is this kind
of mystery to
Cartesian dualism that
never gets fully explained.
And so the theory is
ultimately unsatisfying
and doesn't explain what
it's trying to explain.
The next problem with
dualism is that it
seems to just take for
granted that minds are free
and bodies are determined.
So one of the characteristics
of the physical realm
is that everything
in the physical realm
is subject to physical laws--
laws about gravity,
laws about magnetism,
laws about attraction,
or whatever.
But minds don't work like that.
And so the problem for people
who deny Cartesian dualism
or dualism of any
sort is to explain
how a completely physical
system could be free.
So if all I am is a
body and I believe
that I freely make
choices in my mind
and my mind is simply
just an aspect of my body,
I need to explain how that can
exist, how that can happen.
However, the criticism
goes like this, yeah,
but Cartesian dualism
is not off the hook
either, that it's just sort
of assumed that minds are free
and that bodies are determined,
but it's never really explained
how minds are free.
There doesn't seem to
be any room for freedom
in Descartes' picture.
The third problem is
the so-called problem
of other minds.
We take it is as that not
only that I have a mind,
but that you have a mind, right?
So the contents of my mind kind
of immediately noble to me,
but when I see you
walking around,
I see your body doing
certain gestures,
I sort of just take
it for granted.
I take it as an obvious
point about reality
that those gestures and
those bodily movements
are connected to a mind.
But if Cartesian
dualism is true,
it seems to lead us to a kind
of skepticism about other minds.
If minds are immaterial and all
we're ever immediately aware
of is either the
contents of our own mind
or perceptions of other bodies,
other kind of physical events
going on, I can never
immediately perceive your mind,
and so I never really know
whether or not you have a mind.
It seems at least just
as plausible to say
that you're a sophisticated
robot, that you are just
a machine--
in other words, you are
a body walking around,
but that you don't have
any consciousness that's
directing that body.
That's called a
philosophical zombie, right?
To put it another way.
Philosophical zombies
are just like us.
Materially or physically,
they're just like us.
But what they lack
is consciousness.
And if Cartesian
dualism says that mind
must be these extra
things, they must
be these immaterial substances
that latch onto our bodies,
but we can never be
aware of them other
than in ourselves-- we
don't know whether or not
there are any other minds.
And so this problem is called
the problem of skepticism
of other minds, or
it's also called
the problem of solipsism.
Solipsism is the view
that only I exist,
only my own unconscious
mind exists, and there
is no other conscious minds.
The fourth problem is related
to the problem of other minds.
And it's the so-called problem
of the individuating minds.
And it goes like this.
Even if I could establish
that there are other minds,
I have no way of individuating
which mind is mine
and which mind is yours.
If we have physical
objects, we can kind of
distinguish one from the
other, because they take up
different space, even if
they look exactly the same.
So if I have two calculators
and they look exactly the same,
they have exactly the same
qualities except one of them
is in my right hand and one
them is in my left hand,
that I can count
them-- one, two.
I clearly have two things.
But if I had a series
of minds, and let's
say we all go to a
retreat where we're
going to sit down at
some temple somewhere.
We're going to meditate, and we
become masters at meditation,
and so we can clear all
the contents of our minds,
except we are all meditating
on the candle that's
burning in front
of us, so we all
have this sort of
identical image of a candle
burning in our mind's
eye, and that's
the only thing
that's in our mind,
then we have a
bunch of minds that
have no contents other than this
exact same sort of perception
or image.
Well, how would we
count the minds?
If they all have
the same qualities,
there's no difference
in that respect.
But we can't count them
in terms of locating them
in different spaces.
We can't say that one
mind is over there
and one mind is over here, one
mind is in the back of the room
and one mind is in
the front of the room.
Why?
Because minds, according
to Cartesian dualism,
are not material.
They don't take
up physical space.
They're not locatable in space,
so you can't have one mind here
and one mind there, because
minds aren't anywhere.
And so you would have this
weird kind of phenomenon
where you wouldn't
be able to count
one mind next to another mind.
The problem of
individuating minds,
then, gives rise to a
kind of general skepticism
about physical reality
in general, right?
So what this criticism says
is that Descartes never
fully establishes the
existence of physical things,
and that it's going to
be a problem for him,
because sort of obviously,
physical things exist.
And if there's
sort of difficulty
in establishing that,
then it shows you
that your theory is kind
of off on the wrong foot
to begin with.
And the sixth criticism
is about sleep.
If it's the case that we
are kind of mental entities,
what happens to us
when we're deep asleep
or when we're unconscious?
Descartes would seem to have
to say that we don't exist.
And of course, he
did say that, which
is why, for Descartes,
every time we were asleep,
he thought we were at least
a little bit conscious.
In other words, for Descartes,
when you're sleeping,
you're always dreaming
a little tiny bit
so that there is always some
kind of mental event going on.
Because if there
weren't, then it
would be like you
didn't exist at all.
And that seems sort of absurd.
Well, we know now
that there are moments
where we're not conscious at
all, that we're in a coma,
or deeply asleep.
And we don't believe that we
don't exist during that time.
We don't even
believe that our mind
doesn't exist during that
time, because our body exists.
And our body still
has the potential
to do all the interesting things
that bodies do in fact do.
They may think and perceive
and hope and wish and want
and dream and whatnot.
And so even if you're
not doing it right then,
you have the capacity to do it.
And so you exist through
those moments of deep sleep
or moments of unconsciousness.
And insofar as Descartes
has a hard time explaining
that shows that
there's something
wrong with his theory.
And then the last criticism,
which is not on the list,
because I don't
think it's really
a criticism of Cartesian
dualism as much
as a criticism of
Descartes himself,
sort of the historical
Descartes, is about animals.
Descartes believed that
animals were simply
sophisticated machines,
that they were just bodies,
that they didn't have a
mind, that they didn't
have conscious experiences.
So when a dog sort of
yelps out when you kick it,
it's just sort of a
physical kind of response,
but it's not because of a
conscious experience of pain.
And that legacy of believing
that animals were not
conscious sort of led to just
a long and proud tradition
of people doing all kinds
of terrible experiments
on animals.
So people who are in the
animal rights movement really
look back and kind of lament
the fact that Descartes didn't
believe that animals were
conscious at all, because it
really gave them an
excuse to do whatever they
wanted to to animals without any
concern for their well-being.
But I don't have it on
the list of criticisms,
because I think it's a kind
of idiosyncratic aspect
of Descartes itself.
And you could be a Cartesian
dualism-- in other words,
you could believe in
Descartes' theory,
and then just apply
it to animals.
I mean, you could
just say animals,
too, have immaterial
souls or immaterial minds,
just like people do.
And so you could just sort of
update the theory that way.
You wouldn't really be faced
with the same kind of problem.
So it's sort of a
problem for Descartes,
the historical Descartes,
but it's not really
a problem for Cartesian
dualism as a theory.
So it's not included
on the list.
It's just something
that deserves mention.
But these other
problems really are
problems for Cartesian dualism.
And the first one is certainly
the biggest one and the hardest
problem to solve, but the other
ones are no walk in the park
either.
So because of these
criticisms, it
seems like we're
going to have to turn
to another type of theory.
So the next thing
that we'll look at
is a theory of monism,
which, as the name implies,
is a kind of direct
rejection of dualism.
And monism says that
there's only one
kind of thing in the universe.
So we'll leave it at there.
That's Cartesian dualism.
One response to the
mind body problem.
And we'll look at other
theories as we go.
As always, post your
complaints, post your questions,
post your criticisms,
and we'll help
you get through it as we go.
Have a good week.
