8
Res Cogitans and
Dualism
1
The immateriality of the soul

Doubt
I can doubt whether I have a body, but I cannot
doubt that I am or exist.
This argument, though, is invalid (see Arnauld’s
objection CSM II: 139).
From the fact that I doubt that something possesses
a given property it doesn’t follow that this very thing
lacks it.
2

The method of doubt concerns one’s subjective
perception and this does not prevent physical
properties to be essential parts of a thing.
Thus from the fact that I can doubt about me having a
body and that I cannot doubt that I am thinking it does
not follow that the soul is immaterial.
From “I doubt p & I cannot doubt q” it doesn’t follow
that q is not p.
E.g.: From “I doubt that 2+2=4 & I cannot doubt that
3+1=4” it doesn’t follow that 2+2 is not 3+1.
3
I said in one place that while the soul is in doubt about the
existence of all material things, it knows itself preacise tantum—‘in
the strict sense only’—as an immaterial substance … I did not at
all mean an entire exclusion or negation, but only an abstraction
from material things; for I said that in spite of this we are not
sure that there is nothing corporeal in the soul, even though we
do not recognize anything corporeal in it. (Appendix to Fifth
Objections and Replies; CSM II: 276)

Thus, the Cartesian doubt cannot constitute a proof of
the immateriality of the soul.
4
The argument from clear and
distinct perceptions

The arguments which should prove the immateriality of
the soul is known as the “Argument for Clear and
Distinct Perceptions”.
I can clearly and distinctly perceive the mind apart from
body (see fifth meditation).
Arnauld suggested that this argument is similar to the
doubt argument (see CSM II: 142).
5

Arnauld’s argument
One can clearly and distinctly perceive that a triangle
has a right angle and yet not clearly and distinctly
perceive that it has the Pythagorean property. But even
God could not create a right-angled triangle which lacks
it.
Descartes’ reply consists in arguing that neither the
triangle nor its property can be seen as a complete
thing, while the mind and the body must.
6

A complete thing is a substance that can exist on its
own.
Since in my thinking I can conceive the mind/soul to
subsist independently of physical properties it is
perfectly conceivable that God created my thinking
substance without creating the physical ones.
Hence the physical attributes do not belong to the
essence of the soul/mind.

The concept of mind is complete insofar as one is
aware of one’s thinking. And this is sufficient for one to
exist with this attribute and this alone. Thinking is the
only necessary property of the mind.
7
The Divisibility Argument

The mind and body are mutually exclusive. Being
extended the body can be divided while the mind is
indivisible.
There is a great difference between the mind and the body
inasmuch as the body is by its very nature always divisible
while the mind is utterly indivisible. For when I consider the
mind, or myself in so far as I am merely a thinking thing, I am
unable to distinguish any part within myself; I understand myself
to be something quite single and complete. Although the whole
mind seems to be united to the whole body I recognise that if a
foot or an arm or any other part of the body is cut off nothing
has thereby been taken away from the mind. (Sixth Meditation;
CMS II: 59)
8

But, what if we take away the brain?
Descartes circumvents this problem in concentrating
on pure thought (he recognises that some mental
activity such as imagination and sense-perception
depends on the brain), e.g. thoughts of abstract objects.
Even if the body is destroyed, the mind or soul would
not be harmed: it would merely leave the body. The
soul/mind is immortal.
This doctrine, though, has already been established a
priori: it does not rest on the divisibility argument.
9
[T]his power of imagination which is in me, differing as it does
from the power of understanding, is not a necessary constituent
of my own essence, that is, of the essence of my mind. For if I
lacked it, I should undoubtedly remain the same individual as I
now am; from which it seems to follow that it depends on
something distinct from myself. … the difference between this
mode of thinking and pure understanding may simply be this:
when the mind understands, it in some way turns towards
itself and inspects one of the ideas which are within it; but
when it imagines, it turns toward the body and looks at
something in the body which conforms to an idea
understood by the mind or perceived by the senses. (Sixth
Meditation; CSM II: 51)
10
The immortality of the soul

Main Argument
Phase one
Prem. 1: If I can clearly and distinctly understand A
apart from B and B apart from A, then God could have
created one without the other, and A cannot depend on
B for its existence, or B on A.
Prem. 2: I can clearly and distinctly understand myself
as a thinking thing apart from body, and a body as an
extended thing apart from thought.
Preliminary Conclusion: God could have created my
mind in such a way that it does not depend on any
body.
11
Phase two
Prem. 3: God could have created my mind in such a
way that it does not depend on any body.
Prem. 4: If A could have been created to be
independent of B, A can exist when B no longer exists.
Prem. 5: When I am dead, my body (as such) will no
longer exist.
Conclusion: I can exist when my body is dead.

This does not prove, though, that the Soul survives
after the death. It merely proves that it can survive it.
12

Critique
(Cf. Dan Scotus) Some predicates can be conceived
apart from one another and, yet, they cannot exist apart
from one another:
E.g.: divine justice and divine mercy; it is impossible for
God to be just and not merciful as it is impossible for
Him to be merciful without also being just.

Reply
For it to be the case that we can understand two things
distinctly and separately, they must really be entities in
their own right.
13

Imagination
The ability to employ imagination suggests the presence
of the body. If there can be thought without
imagination, as Descartes suggests, there can be
thought without a body.
Imagination, like perception, is not essential to a
subject. Thus, if the souls is immortal it does not
involve imagination and perception; it merely requires
intellectual understanding.
14
The Mind-Body divide

Descartes’ Aim
To prove that the mind and the body are
1. real subjects
2. numerically distinct entities
3. can exist without the other
15
Identity

Leibniz’s Law and the Identity of Indiscernibles
Leibniz’s law
a = b  (F) (Fa  Fb)
If a and b are identical then each property of a must
also be a property of b and vice versa.
16
Identity of indiscernibles
(F) (Fa  Fb)  a = b
This is the converse of Leibniz’s law and states that if
every property of a is also a property of b and vice versa
(i.e. there is no discernible difference between them),
then a and b are identical.
If a and b have all properties in common, then a and b
are identical.
17

Thus.
If MIND and BODY have all properties in common,
then MIND = BODY
If MIND and BODY differ in some property, then
MIND  BODY
18
Mind vs. Body: an Epistemological
Distinction

The mind (x) and the body (y) are distinct =df.
x and y are distinct insofar as x and/or y can be
conceived/understood without each other.
[F]or establishing a real distinction it is sufficient that two
things can be understood as ‘complete’ and that each one
can be understood apart from the other. (Reply to Arnauld;
Fourth Set of Replies; CSM II: 156)
19

Criterion for Distinctness: Clear and Distinct Ideas
Descartes’ criterion of distinctiveness is
epistemological.
Yet, since clear and distinct ideas must reflect the true
nature of things, distinct ideas reflect distinct
substances.

Main question
How can ideas be distinct and thus represent different
substances?
20

Answer
Descartes draws a comparison between mental intuition
(perception) and seeing with the eyes
Indeed there are very many people who in their entire lives never
perceive anything with sufficient accuracy to enable them to
make a judgement about it with certainty. A perception which
can serve as the basis for a certain and indubitable
judgement needs to be not merely clear but also distinct. I
call a perception ‘clear’ when it is present and accessible to
the attentive mind—just as we say that we see something
clearly when it is present to the eye’s gaze and stimulate it with
sufficient degree of strength and accessibility. I call a perception
‘distinct’ if, as well as being clear, it is so sharply separated
from all other perceptions that it contains within itself only
what is clear. (Principles of Philosophy 45; CSM I: 207-8)
21

Direct Mental Apprehension
Descartes’ account of knowledge is thus based on
direct mental apprehension.
Mental intuition goes proxy for mental
acquaintance/grasping.
In discussing the “action of the intellect by mean of
which we are able to arrive to the knowledge of things
with no fear of mistake” (Rules for the Direction of the
Mind; CSM I: 14), Descartes recognizes two
intellectual actions: intuition and deduction.
22

Intuition
By ‘intuition’ I do not mean the fluctuating testimony of the
senses or the deceptive judgement of the imagination as it
botches things together, but the conception of a clear and
attentive mind, which is so easy and distinct that there can
be no room for doubt about what we are understanding.
Alternatively, and this comes to the same thing, intuition is the
indubitable conception of a clear and attentive mind which
proceeds solely from the light of reason. … Thus everyone
can mentally intuit that he exists, that he is thinking, that a
triangle is bounded by just three lines, and a sphere by a single
surface, and the like. (Rules for the Direction of the Mind; CSM I: 14)
23

Necessary/Eternal Truth: Depend on God’s Will
They have been created by God and God makes us to
recognize them (following Descartes’ method of
doubt). God could have created other necessary truths;
even the more basic laws of logic could have been
different if God wished so.
All eternal/necessary truth depend on God’s will.
24
[S]ince every basis of truth and goodness depends on his
omnipotence, I would not dare to say that God cannot make
a mountain without a valley, or bring it about that 1 and 2
are not 3. I merely say that he has given me such a mind
that I cannot conceive a mountain without a valley, or sum
of 1 and 2 which is not 3; such things involve a
contradiction in my conception. (Letter to Arnauld, 29 July
1648; CSMK III: 358-9)
25
Arnauld’s Challenge

Arnauld objects that one cannot go from the subjective
fact to an objective fact.
That is, one cannot infer from his subjective state of
certainty or uncertainty concerning a given fact, to the
objective certainty or uncertainty concerning the fact
itself.
Thus once cannot, pace Descartes, infer from the fact
that one is certain about the distinction between one’s
mind and body, to the fact that the mind and the body
are in fact/in reality distinct.
26
How does it follow, from the fact that he is aware of
nothing else belonging to his essence, that nothing else
does in fact belong to it? I must confess that I am somewhat
slow, but I have been unable to find anywhere in the Second
Meditation an answer to this question. (Arnauld; Fourth Set of
Objections; CSM II: 140)

Arnauld’s argument
It is not possible for (triangle) T to exist without P (the
square of the hypotenuse is equal the square of the two
sides)
27
[E]ven if I deny that the square on the hypotenuse is equal
to the square on the other two sides, I still remain sure that
the triangle is right-angled, and my mind retains the clear
and distinct knowledge that one of its angles is a rightangle. And given that it is so not even God could bring it
about that the triangle is not right-angled. … But how is my
perception of the nature of my mind any clearer than his
perception of the nature of the triangle? … Although the
man in the example clearly and distinctly knows that the triangle
is right angled, he is wrong in thinking that the aforesaid
relationship between the squares on the sides does not belong to
the nature of the triangle. Similarly, although I clearly and
distinctly know my nature to be something that thinks, may
I, too, not perhaps be wrong in thinking that nothing else
belongs to my nature apart from the fact that I am a
thinking thing? Perhaps the fact that I am an extended
thing may also belong to my nature. (Arnauld; Fourth Set of
Objections; CSM II: 142-3)
28

Arnauld objects to the following
What we seem to conceive of x, we really conceive of x

Arnauld denies Descartes’ epistemic transparency.
Arnauld’s argument rests on the fact that possibility
precedes conceivability.
Thus Arnauld seems to deny this, Cartesian, form of
argument:
If one can conceive of x that it is F and of y that it is
not F, then x  y.
29

Descartes’ way out of this problem is to propose a
reliable, transparent, notion of conceivability. His
notion of ideas should supply what we need:
If one entertains an idea of x being F and an idea of y
being F-less, then x  y

From the distinctness of ideas one can derive the
distinctness of the entities the ideas are about.
But ideas must be ontologically transparent, i.e. there is
no gap between the idea and the thing it is about (cf.
Wittgenstein’s Tractatus picture theory, where we have a
one-one correspondence between words and objects).
30

In order to sustain Descartes’ argument about the
mind-body distinction, the idea of the mind and the
idea of the body must be primitive.
That is, they cannot derivate (by abstraction) from
other more basic and primitive ideas.
31

[T]he idea I have of something is not and idea made
inadequate by an abstraction of my intellect. I derive this
principle purely from my own thought or awareness. I am
certain that I can have no knowledge of what is outside me
except by means of the ideas I have within me … But I think
also that whatever is to be found in these ideas is
necessarily also in the things themselves. So, to tell whether
my idea has been made incomplete or inadequate by an
abstraction of the mind, I merely look to see whether I have
derived it, not from something outside myself which is more
complete, but by an intellectual abstraction from some other
richer or more complete idea which I have in myself … [T]he
idea which I have of a thinking substance is complete in
this sense, and that I have in my mind no other idea which
is prior to it and joined to it in such a way that I cannot think of
the two together while denying the one of the other. (Letter to
Gibieuf 19 Jan. 1642; CSMK III: 201-2)
32

We can even grant Arnauld that, of necessity, one’s
mind coexists with one’s body, i.e. that they are a union
inside a human being.
Yet we can maintain that they are different: the mind is
a thinking thing while the body is an extended thing. As
such they are different substances in which different
attributes inhere.
Thus even if it is not really/actually possible for the mind
to exist without the body it is logically possible—there is a
possible world in which the mind exists without the
body. While the mind is essentially thinking, the body is
not. They are thus numerically distinct.
33

If one entertains a primitive idea of the mind being
essentially thinking and of the body not being
essentially thinking, then the mind differs from the
body.

The idea of the mind reflects that the mind really is: it
is transparent, a de re idea. Descartes is assuming that
when one imagines/thinks about/… one’s own mind
one has direct access to it. In that case, what one is
imagining/is having an idea of/…, is really what it is.
We cannot divorce, as Arnauld’s argument seems to
suggest, the what it is (the res) from its idea. In short,
there is no gap between the idea of mind and the mind.
Primitive ideas are directly representative.
34

There seem to be no difference between the mind (as a
res) and its phenomenological character.
The exercise involved in thinking about one’s own mind
is radically different from the exercise involved in
thinking about an external object.
Two distinct objects/substances (e.g.: XYZ vs. H2O)
may instantiate the same phenomenological properties.
This is never the case when thinking about the mind.
35
The Union Between Mind and Body

Mind-Body Unison
I am not merely present in my body as a sailor is present in
a ship, but that I am very closely joined and, as it were,
intermingled with it, so that I and the body form a unit. If this
were not so, I, who am nothing but a thinking thing, would not
feel pain when the body was hurt, but would perceive the
damage purely by the intellect, just as a sailor perceives by sight
if anything in the ship is broken. … These sensations of hunger,
thirst, pain and so on are nothing but confused modes of
thinking which arise from the union and, as it were,
intermingling of the mind with the body. (Sixth Meditation; CSM
II: 56)
36

The main question, though, concerns the manner in
which the mind is related to the body.
Descartes seems to give contrasting (contradictory?)
answers.
On the one side, he said the soul resides in the brain (the
pineal gland) and on the other side he said that it is
coextensive with the body.
37
It must be realised that the human soul, while informing the
entire body, nevertheless has its principal seat in the brain; it
is here alone that the soul not only understand and
imagines but also has sensory awareness. (Principle of
Philosophy 4. 189; CSM I: 279-80)
My next observation is that the mind is not immediately
affected by all parts of the body, but only by the brain, or
perhaps just by one small part of the brain, namely the part
which is said to contain the ‘common’ sense. (Sixth Meditation;
CSM II: 59)
38

These statements suggesting that the mind-body union
is guaranteed by the pineal gland seem to contradict the
following
[C]lothing, regarded in itself, is a substance, even though when
referred to the man who wears it, it is a quality. Or again, the
mind, even though it is in fact a substance, can nonetheless
be said to be a quality of the body to which it is joined. …
This is exactly the way in which I now understand the mind to
be coextensive with the body—the whole mind in the whole
body and the whole mind in any of its parts. (Sixth Set of
Replies; CSM II: 297-9)
39

How, though, can a non extensive substance (the mind)
be coextensive with an extensive substance (the body)?
Descartes is aware of this problem.
Even though the mind is united with the whole body, it does
not follow that it is extended throughout the body, since it
is not in its nature to be extended, but only to think. (Fifth Set
of Replies; CSM II: 266)
40
30. The soul is united to all parts of the body conjointly
But in order to understand all these things more perfectly, we
need to recognize that the soul is really joined to the whole body,
and that we cannot properly say that it exists in any one part of
the body to the exclusion of the others. For the body is a unity
which is in a sense indivisible because of the arrangement of its
organs, these things being so related to one another that the
removal of any one of them renders the whole body defective.
And the soul is of such a nature that it has no relation to
extension, or to the dimensions or other properties of the
matter of which the body is composed: it is related solely to
the whole assemblage of the body organs. This is obvious
from our inability to conceive of half or a third of a soul, or of
the extension which a soul occupies. Nor does the soul
become any smaller if we cut off some parts of the body,
but it becomes completely separate from the body when we
break up the assemblage of the body’s organs.
…
41
31. There is a little gland in the brain where the soul
exercises its functions more particularly than in the other parts of the
body
We need to recognize also that although the soul is joined to
the whole body, nevertheless there is a certain part of the
body where it exercises its functions more particularly than
in all the others. It is commonly held that this part is the
brain … because the sense organs are related to it ... the
innermost part of the brain, which is a certain very small gland
situated in the middle of the brain’s substance and
suspended above the passage through which the spirits in
the brain’s anterior cavities communicate with those in its
posterior cavities. (The Passion of the Soul; CSM I: 339-40)
42

Sameness of Body
Existence thorough time: our body keep changing, yet
it is the same as the one we got in our infancy.
That remains the same, though, are not the qualitative
properties but its numerical identity. The latter is
granted by the soul. The numerical identity of one’s
body rests on the identity of one’s mind.
43
But when we speak of the body of a man, we do not mean the
determinate part of matter, or one that has a determinate size;
we mean simply the whole of the matter, or one which is united
with the soul of that man. And so, event through the matter
change, and its quantity increase or decrease, we still believe
that it is the same body, numerically the same body. So long
as it remains joined and substantially united with the same
soul … there is no longer in them any part of the matter which
then belonged to them and even though they do not have the
same shape any longer; so that they are only numerically the
same because they are informed by the same soul (Letter to
Mesland 9 Feb. 1645; CSMK III: 243)
44

In the same letter Descartes recognises the ambiguity in
the world ‘body’
I consider what exactly is the body of a man, and I find that this
word “body” is very ambiguous. When we speak of a body
in general, we mean a determinate part of matter, a part of
the quantity of which the universe is composed. In this
sense, if the smallest amount of that quantity were removed, we
would judge without more ado that the body was smaller and no
longer complete; and if any particle of the matter were changed,
we would at once think that the body was no longer quite the
same, no longer numerically the same. (Letter to Mesland 9 Feb.
1645; CSMK III: 242-3)
45

In the Meditations ‘body’ is defined generally.
[[B]y a body I understand whatever has a determinate shape
and a definable location and can occupy a space in such a
way as to exclude any other body; it can be perceived by
touch, sight, hearing, taste or smell, and can move in various
ways, not by itself but by whatever else comes into contact with
it. For, according to my judgement, the power of self-movement,
like the power of sensation of thought, was quite foreign to the
nature of a body. (Second Meditation CSM II: 17)
46
Descartes’ Error

Feelings (cf. Damasio. 1994. Descartes’ Error)
It is wrong to consider the working of the brain and
mind as separate from the working of the body.
The mind is part and parcel of the body.
E.g.: background feelings, i.e. the underlying awareness
of the state that your body is in.
47

Background awareness depends on the various
neuronal and hormonal signals arising from the body
organs (skin, hearth, …) that are sent to and processed
by the brain.
These signals provide a continuous update on the
changes that our body state undergoes.
These background feelings provide our sense of ‘self ’.
48

We process information emanating from our entire
body.
Hence, we wouldn’t be the same person if our brain
were transplanted in another person.
For the body would provide different information.
49

On top of background feelings we also have stronger
feelings arising when we experience emotions in
response to particular events.
New born babies tend to show only primary emotions
(e.g. fear) which are innate and pre-organized.
As we grow we develop and make more use of
secondary emotions which are primary emotions
tempered by experience.
Emotions become associated with particular
experiences. Thus their link with learning.
50

Peptides
Are neurotransmitters produced in the brain.
They are also active in the human immune system and
endocrine system.
Hence, they participate in the constant relationship
between the brain and the body.
51