‘Assess Descartes’ use of doubt and certainty in establishing his
own existence.’
In the first Meditation, Descartes uses his sceptical method of doubt to establish a point of maximum
uncertainty. In the second meditation, he argues that the first certainty is the cogito: that if he thinks, he
exists. In this essay I will consider both stages and argue that Descartes’ scepticism cannot be as extreme as
he supposes.
A sceptic is one who doubts that knowledge is achievable. Unlike classical sceptics, who believed that
knowledge is impossible, Descartes is a methodological sceptic who uses his method of doubt to call into
question all our prior beliefs. He believes that those beliefs rest primarily on the senses and by challenging
them, he will pave the way for establish his rationalist philosophy. The cogito is the first plank of his rationalist
foundationalism. Descartes’ scepticism is therefore hyperbolic or extreme. By the end of the first meditation,
nothing is certain.
The method of doubt works in the following way. You take a belief you have. For example, I might choose the
belief that it is 2 p.m. now. You then ask whether it is possible that your belief could be false by constructing a
sceptic scenario in which it would be. In my case, such a scenario is the following: someone has set all the
clocks in the exam hall to the wrong time along with my watch. Since I cannot tell whether I am in the
sceptical scenario, I cannot be certain that it is 2 p.m. I must therefore suspend judgment. Any belief that
resists the method – for which there is no sceptical scenario – is therefore certain.
Descartes’ scepticism moves in three ‘waves’. The first draws our attention to familiar perceptual errors. The
sun in the sky looks small but is big. The tower in the distance looks round but is square. Descartes recognises
that these errors arise in non-optimal perceptual situations. He asks whether he could be wrong sitting about
whether he is sitting by his fire. He then argues that there is no clear sign to distinguish waking from sleeping.
This calls into doubt all perceptual beliefs but not all beliefs. Just as an artist’s painting of an imaginary scene
draws upon his knowledge of basic elements, so too must dreams draw upon knowledge of what Descartes
calls universal natures or ideas: colours, shapes, numbers and so forth. This leads him to suppose a ‘malicious
demon’ who has the power to induce any thought at all.
Is Descartes right when he says that there are no clear signs by which to distinguish waking from dreaming?
Hobbes argued that we dream about different things than we experience. This is not conclusive though; even
if dreams sometimes present wild scenarios, their content can also be quite mundane. Malcolm argues that it
is not possible to make judgments in a dream as one is by definition passive. So, if you can judge that you are
awake, then you must be. Yet Malcolm ignored the phenomenon of lucid dreaming where the dreamer has
some control of their experiences. Furthermore, even if one can only judge when one is awake, one can have
the indistinguishable experience of judging when one is dreaming. It is sometimes suggested that there is a
test for dreaming. If you throw yourself off a building and you wake up, this proves you were dreaming.
However, for it to be a real test, both outcomes must be verifiable; and the other one is clearly not. Even if
there were a real test, however, it would not help. For one would have to know that one is not dreaming
when performing the test; and since this is what the test is to establish, we find ourselves going in a circle.
Austin argued that dreams feel different to waking experience. It is not clear that they do. Some dreams may
feel strange but, again, some may feel quite ordinary. However, his thought points to a better argument.
Dreaming and waking are different states. The sceptic wants to say that dreaming and waking are
indistinguishable but they must be distinguishable else I could not have learned that they are different. So, if I
understand the concept of a dream, I understand enough to distinguish dreaming from waking. In the same
way, if I can understand that some £5 notes may be counterfeit, I must have been able to distinguish them.
So, by the same logic, I must be able to distinguishing experience of the real world from the illusory, demoncreated world. In reply, even if the argument works, it at most proves that I must have at some time been
aware of a relevant difference but fails to establish there are any differences now. Suppose I learn of
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counterfeit notes by seeing how they lack a watermark. I realise that a better counterfeit could be genuinely
indistinguishable. I therefore cannot tell now whether the note in my pocket is real. The same goes for my
current experience: I could be a ‘better’ dream or part of a ‘perfect’ illusory world.
Descartes argues that the cogito is doubt-proof. The proposition in question is often expressed in the form I
think, therefore I am. It is impossible to suppose I am thinking and that I do not exist. Thinking is essentially
both conscious and subjective; and so if there is thinking, there is a thinking subject I am aware of. The demon
could not fool me into thinking I think but do not exist for there must be a me to make think that I think.
The cogito does indeed seem to be demon-proof: but what does it actually establish? Russell argued that the
argument failed because it was circular. The premise is “I think”: but to suppose this is to suppose the
existence of an I or self, where this is the conclusion of the argument. Russell echoes Hume who argued that
he could not find any self ‘behind’ the flow of ideas to which those ideas supposedly belong. Hume thought
that the self was a fiction. However, even if Hume is right, it does not mean Descartes is wrong. Hume and
Russell are arguing that there is no proof of a ‘thick’ self or substance underlying our ideas. They do not
disprove the existence of that the thin self that may indeed be a fiction. The thin self is nothing more than the
subjectivity of thought. It is impossible to deny, as Kant observed, that thoughts are subjective in this way. We
have to use the form ‘I think…’ as our experience is one in which thoughts and experiences are unified. I
cannot report my situation as one in which there is a sensation of coffee and a desire to stop writing because
there is nothing to indicate they are occurring in the same mental space. I have to say “I have a sensation and
a desire.”
Descartes moves from cogito ergo sum to sum res cogitans: from the thin to the thick. Even if Hume is right,
the cogito survives as certain. Thinking implies the existence of a subject, being either a real substance with
ideas or a fictional subject constructed out of real ideas.
This said, does Descartes genuinely manage to bring all his beliefs into doubt before establishing it? Descartes
does suggest he does not know the meaning of the words ‘think’ and ‘exist’. He says that these are common
ideas that everyone understands. This raises the question of whether a sceptic could doubt even this. The
problem is that if the sceptic does not claim to know the meanings of the words he is using, he cannot expect
to be understood. He must therefore allow us to know the meanings of our words. This leads us to
Wittgenstein. Wittgenstein argued that both knowledge and doubt require a context. We can examine any
belief to see whether it is true or false only against a background of claims that are beyond knowledge and
doubt. To illustrate this, consider using a microscope to determine whether a cell is of a certain type. One
must assume the microscope is working. One can question this by employing a microscope-checker. But then
one must assume it is working. One can employ a microscope-checker-checker, and so on, but at each stage,
something must be beyond question. Wittgenstein argues that there are background beliefs that together
shape our basic understanding of the world and give meaning to our words. ‘Cars do not grow out of the
earth’ is a fact about cars and one which, if denied, would show someone doesn’t understand the meaning of
‘car’.
This means that the a sceptic who uses a meaningful language must in fact be part of a world in which truths
like these hold and which are known by him. The possibility of a global sceptical scenario, in which all is
illusion, disappears. To this one can add Wittgenstein’s private language argument. It would not be possible
for me to form a language if I experienced an illusory world in which I was the only real language user. A
meaningful word must have objective criteria of application. A subject attempting to classify his private
experiences would lack such criteria and be unable to know whether he was applying his terms correctly. If
the sceptic is a language-user, he must be one amongst many. It follows that the sceptical scenario in which I
which I am the sole language user is impossible. So, the existence of a meaningful language means that the
existence of a world of things and language-users I am part of cannot be called into doubt.
In conclusion, Descartes does manage to establish the cogito but he was wrong to think that the method of
doubt eliminates all but it as a certainty. The sceptic cannot doubt the existence of the world to which he
belongs on pain of making his language meaningless.
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