Descartes and Locke




The Move from Doubt to Certainty; A Look
at the Theories of Descartes and Locke

Descartes is interested in the certainty of his
existence and the existence of other people and things.
Descartes’ beliefs vary from those of Socrates. Descartes
argues that knowledge is acquired through awareness and
experience. Using this approach, Descartes moves through
doubt to certainty of his existence. He asks himself
various questions about the certainty of his existence and
solves them through clear thought and logic. Using this
method Descartes establishes doubts to be truths and by the
end of the book, he has established that he does indeed
exist. In this paper, I will show how Descartes moves
through doubt to certainty. I will explain how Descartes
uses the cogito, proves the existence of God and what that
means to his existence. I will also discuss the general
rules of truth that Descartes establishes.
In the First Meditation Descartes begins to examine
what is certain and what is doubtful. Descartes wants to
establish that his knowledge is certain and not doubtful.
He states,

...I had accepted many false opinions as being
true, and that what I had based on such insecure
principles could only be most doubtful and
uncertain; so that I had to undertake seriously
once in my life to rid myself of all opinions I
had adopted up to then, and to begin, and to begin
afresh from the foundations, if I wished to
establish something firm and constant in the
sciences.(Descartes 95)

By this Descartes means that he wishes to establish a
foundation for his knowledge based on certainty instead of
doubt. Descartes first looks at the senses. This is
important because the senses are the first thing to cause
doubt. He focuses on the perception of things. He says that
things far from him, in the distance, give him reason to
doubt their certainty, while things that are close to him
are indubitable and he is clear about their certainty.
However, Descartes realizes that dreams pose an
obstacle to his beliefs. Even up close, dreams can be
indubitable. Descartes believes that if a person has had a
dream that was so intense that the person could not
determine it form reality, then they have reason to doubt
objects that are close to us and appear to be indubitable.
In order to resolve this problem, Descartes suggests that
one must examine whether they are dreaming or not.
Descartes realizes that he can not rely on his senses
anymore to give him dubitable truths. He turns to find
something that is indubitable. Descartes tries to use
science as a foundation for truth. He discards physics,
astronomy, and medicine because all three of them rely upon
the senses. “...we shall not be wrong in concluding that
physics, astronomy, and medicine, and all the other sciences
that depend on the consideration of composite things, are
most doubtful and uncertain...”(Descartes 98). However,
Descartes finds that such things as geometry and arithmetic
can be trusted because their are no senses involved. They
are based upon logic.

“...whether I am awake or asleep, two and three
added together always makes five, and a square
always has four sides; and it does not seem
possible that truths so apparent can be suspected
of any falsity or uncertainty”(98).

However, Descartes finds reason to even doubt this.
The only thing that could makes these truths dubitable is
through the intervention by an Evil Deceiver (God).
Descartes cannot prove that God is good and has to
acknowledge that God has the power to deceive. Therefore,
Descartes must doubt all things until he can prove their
certainty. Descartes comes to call this doubt Universal
Doubt.
In the Second Meditation, Descartes examine the
existence of himself. He concludes that if he cannot prove
something exists then how does he know with certainty that
he exists. It is his doubt of his existence that Descartes
uses to prove his existence. Descartes realizes that if he
is able to doubt then he does indeed exists. He take the
approach that, “I think therefore I am” to establish a
certainty that he exists. This idea also known as the
cogito becomes the central point that Descartes will use for
the remaining of his meditations. Descartes affirms his
existence every time he thinks, doubts, or is
persuaded(Descartes 103). Descartes affirms that if there is
an Evil Deceiver then Descartes must exist because in order
for God to deceive, Descartes he must first exist.
Although, Descartes has proved his existence he can
only prove it in the mental capacity. He does not know for
certain that he exists in the physical form. The only way,
at this time, that Descartes can prove the existence of his
body is through his senses.