In the last session, we studied a philosophical system called Stoicism. It is a system
because in tackling the question how we ought to live, it connects the answer to the
conceptions about what the universe is, about who we are and our place in the
universe. We didn’t go into detail about what the Stoics think about human nature
apart from mentioning that they believe humans share reason with God. In this
session, we therefore will take a closer look at the question about who we are or about
what human nature is.
Since ancient times, human beings have been thinking of themselves as not just
physical beings but also mental beings. In thinking so, they also believe we have a
soul which is the source of our mental life; and this soul can be separated from the
physical world. Thus when we die, it is our bodies that disintegrate, our souls live on
and might even be immortal. Do we have a good reason to believe this? This is one of
the main problems of philosophy that remains to be solved. It is called the mind-body
problem.
The Mind-Body Problem
In everyday speech, we usually distinguish between our mind and our body. Though
we are gravely sick and our body is weak, we try to uphold our spirit and keep our
spirit strong. Some cancer patients who suffer a lot of pain talk about the technique of
separating the mind from the body so that when they are in pain, their minds are
shielded from the pain i.e. they still feel good even though the pain is excruciating. A
woman might complain to her lover that he only wants her body (he only wants to
have sex with her and is not interested in love or commitment). We do talk about
sharing the spirit, but we never talk about sharing the body.
In other words, we feel we have a mental life apart from our body. That is to say,
when we observe ourselves, we can make a distinction between mental states and
physical states. Mental states are our consciousness and our various feelings and
thoughts. Our mental life is composed of mental states; we have hopes, desires, fear,
ambition etc. which we can feel. Mental states are private in the sense that we can’t
feel other people’s hopes, desires, and so on; even though we can observe their
behaviors which express their hopes and desires etc. Other people also cannot directly
observe our mental states and processes. Body states are our actions, movements,
appearances, they include processes that go on inside our body. These states are
public in the sense that they can be observed by anybody. Even processes that go on
inside our body can, theoretically, be observed with medical instruments. But we
can’t do the same with our mental states and processes. Thus we feel we have an inner
life completely different from our observable physical life. This is the basis of our
common-sense belief that the mind is distinct from the body. If this is true then it is
possible that death only affects the body, the mind might live on maybe a little while
longer, or maybe forever. A person who holds this kind of belief is a dualist: she
believes that human beings are composed of two distinct elements – the mental and
the physical. This kind of belief is called dualism.
Of course there is an alternative way of thinking. Our mental states might just be
identical with our brain states. Our pain for example might be identical with a certain
brain process. This is why when we take a pain killer which can only affects our body,
the pain is gone. Our fear and anxiety too might be blocked by some drugs which act
on our brain. Nowadays, scientists are trying to map the brain in order to identify
which part of the brain is responsible for a particular mental state. They hope that one
day they will be able to link each and every mental state to a particular brain state.
When that day comes, they think they can claim that all mental states are explained by
brain states and thus the mystery of the mind is solved. If this understanding is
correct, then the mind is not distinct from the body. Our language which distinguishes
the two is just a manner of speaking, it doesn’t reflect reality. Our common-sense
belief deceives us. A person who holds the belief that everything including the mental
can be explained in physical terms is a physicalist, and this kind of belief is called
physicalism.
Here’s a puzzle to think about. If you get a brain transplant (still a remote
probability), do you have a new brain, or does somebody else move into your body?
In the first case you are still yourself with a new brain, in the latter case, only your
body (minus the brain) is still alive, you as a person is dead and gone and somebody
else comes to inhabit your body. Your answer will determine whether you are a
dualist or a physicalist.
If we take the two ways of thinking about the mind-body problem above as
arguments, then both are not convincing. For the first way of thinking to be
convincing, it has to show that the unique characteristics of the mind must be such
that no physical things can have them. To say that mental states are different from
physical states is not enough. It is possible that physical states can produce
phenomena that appear different from them.
As for the scientific view, even if the brain-mapping is successful, the other side can
claim that it doesn’t prove a thing. They would say that the mind is a distinct entity
from the physical body, and it controls the body through the interaction with the brain.
When scientists pair every mental state with a brain state, what they observe is the
results of the interaction between the two entities. If one day we can construct an
artificial human being with a brain, it may behave like real humans, but it wouldn’t be
able to think and feel the ways humans do because it lacks a mind.
As I mentioned earlier, philosophy tries to go deeper that the common sense level.
The mind-body problem becomes a philosophical issue because philosophy is
interested in exploring the reasons underlying these two positions. Philosophers
defending each position try to give reasons to back up their belief, and at the same
time try to use logic to criticize the other position. We will take a look at one of the
most famous reasoning used to justify the conviction that the mind is distinct from the
body. The argument belongs to a French philosopher named Rene Descartes (1596 1650). Descartes is regarded by all as one of the greatest philosophers. Again, to
emphasize what I have said before, to regard a philosopher as one of the greatest does
not mean he is right. Very few philosophers nowadays think Descartes’ reasoning is
valid, but his elaborate attempt is mesmerizing and shows the great mind behind it.
That’s enough to regard him as one of the greatest. After Descartes, we will consider
an attempt to prove that machines can think, which implies that human beings who
pride themselves on the ability to think might just be machines.
Descartes' Project
In the 17th century, Descartes was well known both as a scientist and a philosopher;
today his fame as a scientist has diminished but he is known as one of the greatest of
modern philosophers. In his days, his scientific works included physics and geometry.
In the 17th century there occurred a scientific revolution begun by the works of
Copernicus, culminating in the works of Galileo and Newton. The reliance on
observation, new instruments, and the testing of hypothesis by means of experiments
generated tremendous advance in knowledge of the universe. In this exciting
atmosphere, Descartes wanted to ascertain that people's belief (at that time) that
knowledge of the universe was within grasp was not an illusion. In the past, before
Galileo and Newton came along, people thought they had knowledge of the universe
but then it was proved they were wrong. They suffered an illusion before and so it
could happen again. Descartes’ assumption was that a body of knowledge must be
built upon the correct foundation. His quest was to find this foundation and showed
that it guaranteed that the knowledge that people believed they had was not an
illusion.
Central to Descartes' project is the method of doubt (which is explained below). He
proposes that any beliefs that can be doubted must be supposed to be untrue. By
casting doubt upon every belief, he in fact is asking whether we can know anything at
all. In other words, Descartes starts his philosophical system by asking the fourth
basic question in philosophy (see the second lecture). From the answer to this
question, he goes on to answer the second and the third questions. Compare this to the
ancient Stoics who begin their system by asking the third question.
Descartes’ Argument
We will take a look at this argument section by section.
…I had long before remarked that, in relation to social conventions, it is sometimes
necessary to adopt, as if above doubt, opinions which we discern to be highly
uncertain, as has been already said; but as I then desired to give my attention solely
to the search after truth, I thought that a procedure exactly the opposite was called
for, and that I ought to reject as absolutely false all opinions in regard to which I
could suppose the least ground for doubt, in order to ascertain whether after that
there remained aught in my belief that was wholly indubitable.
What Descartes means is that when it comes to opinions about morality and
conventions (translated from les moeurs in French) which are concerned with actions
towards other people, even though we have doubts about them we still have to adopt
these opinions and act according to them in order to be able to live with other people.
It is a practical necessity. But in the quest after truth, he wants to adopt a completely
different attitude. He will suppose that any beliefs that can be doubted are false. The
idea is to find a belief that cannot be doubted at all.
Descartes doesn’t mean to say that everything that can be doubted is false, he only
wants to suppose at this stage that what can be doubted is false. He also doesn’t really
doubt everything; he’s talking about what can be doubted. The idea is to discover
what is so certain that it cannot be doubted at all. The motivation behind this is to
answer the challenge of skepticism, a school of thought that is a thorn in the side of
philosophers since ancient Greece. Skepticism believes that human beings cannot
know reality, that is, cannot have knowledge. Its basic argument is this:
Knowledge must be certain, that is to say, what is knowledge cannot be
doubted.
Everything can be doubted.
Therefore, we cannot have knowledge.
Descartes accepts the first premise, but wants to challenge the second one. His
strategy is to cast doubt on everything to see if there is anything left that cannot be
doubted. If at least one statement is proved to be indubitable, then the skeptic’s
challenge is met. But that is not enough. If only one statement cannot be doubted, then
the knowledge we have is so little that it means nothing. What Descartes wants is that
from that one indubitable statement, we can infer other statements from it to form a
system of knowledge that encompasses everything.
At this point we have to try to understand what Descartes means by ‘doubt’. In every
day life we doubt whether a statement is true when we do not have an adequate
evidence for it. That means when we accept a statement as true, our criterion is that
we do not have any good evidences against it. The sense of ‘doubt’ that Descartes
uses here is stronger. He is saying that if we do not have a conclusive evidence for a
statement, then there is room for doubt and that statement must not be regarded as
true. By ‘conclusive evidence’ he means it makes a statement impossible to be false.
To understand what this means, please look back at your logic lessons with Acharn
Pratoom; in a valid deductive argument, the premisses provide a conclusive evidence
for the conclusion because if the premisses were true then it would be impossible for
the conclusion to be false. In fact, if you look at the skeptics’ argument above, the
word ‘doubt’ is used in this strong sense. Descartes even goes further to say that he
will suppose that the statement that lacks the conclusive evidence is false. This sounds
unreasonable because it is very strict; for by common sense if a statement lacks
conclusive evidence, we doubt that it is true but we will not go so far as to say it is
false. However, Descartes’ purpose is to once and for all refute skepticism; his
strategy is that given this very strong assumption, if he can satisfy this criterion, then
the skeptics have no room to argue against him. His doubt is called the
methodological doubt, as opposed to the kind of doubt we have in everyday life.
But what if he could find only a handful of statements which satisfy this criterion;
even worse, what if he could find only one! (To anticipate a bit, he finally found only
one.) The skeptics would say ‘we grant you these few statements, but if these are all
one can know then it is not much better than knowing nothing’. But Descartes would
not be deterred by this; he believes if he could find only one then his project is
successful. What is the assumption behind this confidence? Descartes believes that
our knowledge has a hierarchical structure. A claim to knowledge, for example, the
earth moves around the sun, must be supported by reasons i.e. other claims that have
been shown to be true. These latter claims must themselves be supported by others
that have been shown to be true. This goes on in a string of conclusions and premises.
But it cannot go on indefinitely otherwise it would be absurd. The chain has to stop
somewhere, and that somewhere is a belief that is so certain and evident it needs no
support. This belief (or set of beliefs) is the foundation of our knowledge. Without it
our claim to knowledge is invalid. From this belief (or set of beliefs) we can build up
the whole edifice of knowledge. It is this quest for the foundation that leads Descartes
to adopt the above method. He believes that the methodological doubt will lead him to
discover the foundation of our knowledge.
We continue then with the next passage:
Accordingly, seeing that our senses sometimes deceive us, I was willing to suppose
that there existed nothing really such as they presented to us; and because some men
err in reasoning, and fall into paralogisms, even on the simplest matters of geometry,
I, convinced that I was as open to error as any other, rejected as false all the
reasonings I had hitherto taken for demonstrations;
In this passage, Descartes questions the reliability of our sense-perception and our
reasoning. His argument is that our senses and reason sometimes give us false beliefs,
therefore they are not reliable. Of course at other times they give us what we think are
true beliefs; but the fact that they cannot give us true beliefs every time is enough to
deem them unreliable. If they are unreliable, then there is room for doubt and thus the
statements we get from our senses and reasoning are not certain. Since these two
faculties are believed to be the basis of human knowledge i.e. it is believed that
human beings acquire knowledge using these two faculties, Descartes has cast a wide
net of doubt over the whole realm of human knowledge. There seems to be nothing
left that cannot be doubted.
The above argument against sense perception serves to illuminate what I tried to
explain above about Descartes’ sense of the word ‘doubt’. We all know that
sometimes our senses deceive us. But if I see a table in front of me, and there is
enough light, and I am awake, and I am of the right mind, then there is a very high
probability that there is really a table in front of me. But as you learnt in your logic
class, it is possible for a statement that has a very high probability of being true to be
false. This is what Descartes means by there is room for doubt, and thus according to
his strategy, any data from sense perception are false.
and finally, when I considered that the very same thoughts (presentations) which we
experience when awake may also be experienced when we are asleep, while there is
at that time not one of them true, I supposed that all the objects (presentations) that
had ever entered into my mind when awake, had in them no more truth than the
illusions of my dreams.
Worst of all, he claims that what we can experience when we are awake can also be
experienced when we are asleep. Put it in another way, while we are dreaming, we
think everything that is happening is true, and that is not different from what we think
when we are awake. So how do we know that we are not now dreaming? We think we
have knowledge when in fact we are just dreaming! To make it clearer and even more
striking, I’ll quote a passage from his famous work, Meditations on First Philosophy,
which was published after Discourse on the Method.
How often have I dreamt that I was in these familiar circumstances, that I was
dressed, and occupied this place by the fire, when I was lying undressed in bed? At
the present moment, however, I certainly look upon this paper with eyes wide awake;
the head which I now move is not asleep; I extend this hand consciously and with
express purpose, and I perceive it; the occurrences in sleep are not so distinct as all
this. But I cannot forget that, at other times I have been deceived in sleep by similar
illusions; and, attentively considering those cases, I perceive so clearly that there
exist no certain marks by which the state of waking can ever be distinguished from
sleep, that I feel greatly astonished; and in amazement I almost persuade myself that I
am now dreaming.
One tends to think this is absurd. “I just woke up this morning so I know that now I’m
awake”, one might say. But it could be that in saying this he was asleep dreaming that
he was reading the above passage and saying why it was absurd. “No matter”, one
might retort, “I can’t be dreaming all the time, some other times I am surely awake”.
For this reply, Descartes asks us to consider the following scenario:
IwillsupposethereforethatnotGod,whois supremelygoodandthesourceoftruth,
butrathersomemaliciousdemonoftheutmostpowerandcunninghasemployedall
hisenergiesinordertodeceiveme.Ishallthinkthatthesky,theair,theearth,
colours,shapes,soundsandallexternalthingsaremerelythedelusionsofdreams
whichhehasdevisedtoensnaremyjudgement.
Imagine that in the beginning there was nothing but the Demon with all the powers
we usually attribute to God. He felt lonely and, being mischievous, he thought of a
joke to amuse himself. He said “Let there be a person” and there was a person and I
am that person. Then he put all kinds of delusions of dreams into me deceiving me
into thinking that apart from me things external to me really existed. In other word, in
the universe, only the Demon and I exist.
You think this is a fantasy, an absurdity. Please convince me that it is impossible or
inconceivable and I will give up teaching philosophy for good.
At this point, the situation seems hopeless. It seems that if we might be dreaming,
then everything is subjected to doubt and the quest for the foundation is futile. And
yet…
But immediately upon this I observed that, whilst I thus wished to think that all was
false, it was absolutely necessary that I, who thus thought, should be somewhat; and
as I observed that this truth, I think, therefore I am (COGITO ERGO SUM), was so
certain and of such evidence that no ground of doubt, however extravagant, could be
alleged by the sceptics capable of shaking it, I concluded that I might, without
scruple, accept it as the first principle of the philosophy of which I was in search.
The hopeless situation, instead of condemning us to doom, coughs up the foundation
we are looking for. If I doubt everything, since doubting is a kind of thinking, then it
is beyond doubt that I who think must exist. ‘I think, therefore I am’ is thus certain
beyond any doubt. Doubting this only makes it even more certain that it is beyond
doubt. So Descartes has discovered the foundation of our knowledge at last.
Nevertheless, the indubitable fact that I exist is so trivial and has so little content that
it does not seem to be able to provide the foundation for the whole edifice of
knowledge. Here Descartes’ genius comes into play; with this slim basis he tries to
put the whole of human knowledge upon it.
In the next place, I attentively examined what I was and as I observed that I could
suppose that I had no body, and that there was no world nor any place in which I
might be; but that I could not therefore suppose that I was not; and that, on the
contrary, from the very circumstance that I thought to doubt of the truth of other
things, it most clearly and certainly followed that I was; while, on the other hand, if I
had only ceased to think, although all the other objects which I had ever imagined
had been in reality existent, I would have had no reason to believe that I existed;
Now that I know beyond doubt that I exist, so the next question is what is this ‘I’. The
indubitable fact that I exist does not prevent me from doubting that my body exists.
This seems absurd, but in fact it is a logical conclusion of what I have found. If I can
doubt that external things exist, since external things include bodies of other people,
therefore my own body can also be doubted. Nevertheless, even when I doubt that my
body exists, this doubt implies that I who doubt must exist. What then is this ‘I’?
From all the considerations above, it is evident that if I should ever cease to think,
then there is no reason to think that I exist. Therefore in the fact that I exist, the nonexistence of the body is not essential i.e. I can doubt that my body exists without
shaking the fact that I exist because as long as I think so, I who think must still exist.
The thinking itself is essential, without it there’s no reason to think that I exist. That
is, in ‘I think, therefore I am’ it’s the thinking that assures my existence, my body
doesn’t.
I thence concluded that I was a substance whose whole essence or nature consists
only in thinking, and which, that it may exist, has need of no place, nor is dependent
on any material thing; so that " I," that is to say, the mind by which I am what I am, is
wholly distinct from the body, and is even more easily known than the latter, and is
such, that although the latter were not, it would still continue to be all that it is.
The conclusion is then clear. My being (Descartes uses the word ‘substance’) is
identical with my thinking and thus with my mind (since the mind does the thinking).
Because I can doubt that my body exists but I can’t doubt that my thinking exists, the
mind is distinct from the body and is independent from it in the sense that even if the
body didn’t exist, the mind would remain what it is.
From this point Descartes goes on to base the whole knowledge upon this foundation.
But we will pause here since at this point we are interested in the mind-body problem.
Descartes’ position is called dualism because he argues that the mind is distinct from
the body and that means human beings are composed of two distinct elements.
If you think it’s not valid, you must locate where the problem is. To help you think
about the final part of his argument, I will present it from another perspective. The
argument can be understood like this:
I can doubt that my body exists.
I cannot doubt that I exist.
Therefore I am not identical with my body.
How do the two premises lead to this conclusion? In the Euthyphro, when Plato
points out that ‘god-beloved’ is not identical with ‘pious’, he makes use of the idea
that if two expressions mean the same thing, then one can be substituted for the other
without changing the truth of statements. The principle applies here. If ‘I’ is identical
with ‘my body’, then the two are interchangeable without changing the truth of the
statements where the two occur. But if we substitute ‘I’ for ‘my body’ in the first
sentence, we get a statement that contradicts the second premise which is true. If we
substitute ‘my body’ for ‘I’ in the second premise, then we get a statement that
contradicts the first premise. Plato’s argument is valid, but does it mean Descartes’
argument is valid too?
Problem with Descartes’ Argument
Consider the following argument which has the same form as Descartes’ argument as
stated above.
Kay believes that the evening star is Venus.
Kay believes that the morning star is not Venus.
Therefore, the morning star is not identical with the evening star.
This argument is invalid. How do we know that it is? Remember when you studied
logic with Acharn Pratoom, the definition of deductive validity is that: a valid
argument is that in which if all the premises are true then it’s impossible for the
conclusion to be false. In the above argument, we know for a fact that the conclusion
is false; thus even if all the premises were true, then it would be possible for the
conclusion to be false (the possibility of the conclusion being false is shown by the
fact that it is false). Thus the argument is invalid. In other words, the conclusion does
not follow because both premises are about Kay’s beliefs, but the conclusion has
nothing to do with her beliefs. But the following argument is valid.
The evening star is Venus.
The morning star is not Venus.
Therefore the morning star is not identical with the evening star.
The second premise is false, so is the conclusion. Nevertheless were both premises
true, the conclusion had to follow i.e. the argument is valid. Here’s another example
of an invalid argument.
Bob wants to hear Lady Gaga sing.
Bob doesn’t want to hear Stefani Germanotta sing.
Therefore Stefani Germanotta is not identical with Lady Gaga.
The first and third examples are different from the second example in that they
contain psychological verbs “believe” and “want”, and these verbs are the main verbs
of the sentences. Other psychological verbs include “expect”, “doubt” etc. Whether
the sentence “Kay believes that the evening star is Venus” is true or false depends on
whether Kay believes so or not. If she really believes so, then the sentence is true,
regardless of what the relation between the evening star and Venus is. Thus the
sentence “Ancient people believed that the earth was flat” is true even though the
earth is really round. But in the sentence “The evening star is Venus”, if the evening
star were not Venus, then the sentence would be false, no matter what people believe
about the relation between the evening star and Venus. To make the first argument
valid, the conclusion must be changed to “Therefore, Kay believes the morning star is
not identical with the evening star”.
When we apply this point to Descartes’ argument, we can clearly see what is wrong
with it. His argument:
I can doubt that my body exists
I cannot doubt that I exist.
Therefore I am not identical with my body.
Contains a psychological verb “doubt”. For the argument to be valid, the conclusion
must be “Therefore I can doubt whether I am identical with my body”, which is not
enough to establish that I am not identical with my body. The argument as it stands is
invalid in the same way as the first and third examples above.
Descartes later on came to be aware of this invalidity, therefore in his major work
called Meditations, he corrected the argument and made it much more complicated
than this. We will take a look at that amended version later.
Descartes’ challenge
What we learnt from Descartes is that in order to prove that the mind is distinct from
the body we have to find a property which the mind has but the body cannot have.
Descartes believes that this property is indubitability: I cannot doubt that I, as the
mind, exist, but I can doubt that my body exists. However, this property does not
qualify because it is not the property of the mind, but the property of the relation of
the knower (I) to the known (my mind). As we have seen before his argument suffers
a logical flaw: the premises contain psychological verbs but the conclusion does not.
In other words, the property that we want is the property that the mind itself has,
independent of the knower. In the case of indubitability, this property is dependent
upon the knower or the doubter.
But Descartes’ argument cannot be dismissed easily. There is something about it
which makes us think twice. When he says ‘I cannot doubt that I, as a mind, exist’ the
knower and the known is the same thing. If that is so, then it means that in the above
sentence, the knower and the known cannot be separated. But in the case of my body,
I can conceive the knower and the known as separated. In fact I can conceive the ‘I’
as separated from everything else outside my mind. Why is this so? It is because I
know my mental states directly and can only know everything else indirectly. One
consequence is that I can prove that I exist but I cannot prove that other people exist.
If a person comes to me and says that “I think therefore I am”, I still have no proof
that this person exists. He might just be a part of my dream. If only I could feel his
feelings and think his thoughts, then I could be sure he has a mind too. But there is no
way that I can do that. This points to the peculiar privacy of my consciousness.
If my consciousness is private but science deals with the publicly provable, then there
seems to be a bifurcation of nature here. Science cannot probe my feelings in such a
way as to feel them. Scientists can map my brain and say that I am now lonely
because their instruments detect a particular signal in my brain associated with the
feeling of loneliness, but they can’t still ‘feel’ my loneliness. The world of
consciousness is closed to science. There is a realm of subjectivity as opposed to
objectivity and it is a mystery to the latter. This of course doesn’t prove that the mind
is distinct from the body for scientists would say that evolution has carried the brain
to the point that it can generate this realm of consciousness; and yet this realm is
dependent upon the physical brain, it is just an epiphenomenon. We don’t know
whether this explanation is correct or not and so far there has been no proof that it is.
If my consciousness is beyond the grasp of science, physicalism will fail in its claim
that everything is physical or can be explained in physical terms. Descartes’ argument
might be invalid, but he is far from being defeated.