Descartes
Descartes is famed by is familiar notion, "I think therefore I am
(Cogito,
ergo sum.)." It is a conclusion he has reached in his second
meditation
after much deliberation on the existence of anything certain.
After he discovers
his ability to doubt and to understand , he is able to
substantiate his
necessary existence as a consequence. What we doubt or
understand may not
ultimately correspond, but we can never be uncertain that
we are in the process
of thought. This idea is a major component in
DescartesŐ proof of the external
world. He relies on the existence of a
non-deceiving God to ensure that an
external world exists after calling it
into doubt by the invocation of the dream
argument. In this argument,
Descartes suggests the possibility that none of our
ideas are caused by
external objects and therefore, such objects may not exist.
He also
raises the idea of a demon that may deceive us and allow us to perceive
what
is not really there. Although he assures himself of his own existence by
his
modes of thought, he remains uncertain of the reality of an external
world.
He doubts whether there is anything of material substance that
provokes thought
within him rather than it being conceived in his mind
completely independent of
anything else. Descartes then considers those
reasons that have inclined him to
believe these material things exist in the
past. "I know by experience that
these ideas do not depend upon my will, nor
consequently upon myself, for often
I notice them against my will... I
feel heat, and therefore I believe that this
feeling or idea of heat comes to
me from something other than myself, namely
from the fire I am near. Nothing
is more obvious than the judgment that this
object (rather than something
else) grafts its likeness on to me." Since
however, he has called upon
anything to be false that provokes any doubt he does
not believe this
explanation to be enough for the proof of the external world.
Relying on
this sort of natural impulse has led him astray in the past, so what
is to
keep it from happening all the time. He also calls upon the dream argument
in
this instance. Ideas come to be in dreams independent of external objects
and
perhaps this is true of ideas when we are awake. It seems that Descartes
finds
it necessary to first establish the existence of a non-deceiving God
before he
can be assured of the existence of anything beyond himself and his
mode of
thought. He does this by the rationalization that his perception of
God is that
of a perfect being. In order for a being to be perfect it must
exist. Since he
himself is an imperfect being, he can not conceive the idea
of perfection on his
own. Therefore, it must have come from some other
faculty that must be perfect,
which is God. It is after his proof of the
existence of God that Descartes comes
to accept that clear and distinct ideas
can be trusted. After this deliberation
his process of coming to the
existence of an external world seems rather direct.
I have the clear
perception that material objects exist. Since I have already
determined that
God is not deceiving me nor my perceptions, my perceptions can
be trusted as
being actual. If my perceptions of material objects and an
external world are
actual, then they must exist. But this external reality is
different from our
reality of thought. It becomes dualistic by the idea of two
separate
substances. Descartes establishes a sort of isomorphic state between
thought,
or the mind, and extension, or matter. The mind takes up no space.
It
consists of the senses and all modes of thought. Matter, however, takes
up
space. It can be divided into smaller and smaller components, but it,
unlike the
mind, has no consciousness. Both, he infers have God as their
source because
God, alone, exists independent of anything else. But, the
substances do not have
any contact with each other. Thought is independent of
matter just as matter is
independent of thought. But, although the two are
indeed completely independent
of each other, there is constant interaction
between the two. This is the
essence of DecartesŐ philosophy of dualism. We
as humans, consist of both and
are therefore, dualistic creatures. We have a
mind and we also take up space.
Both are crucial to our elements of
being, but we will grow old and we can be
physically debilitated. But, so
long we continue to think and have
consciousness, two plus two will always be
four and a mile will still be a
mile.