Descarte\'s Cartesian Doubt

In his first meditation, Descartes sets out with amazing clarity and persistence
to clear himself of every false idea that he has acquired previous to this, and
determine what he truly knows. To rid him of these "rotten apples" he
has developed a method of doubt with a goal to construct a set of beliefs on
foundations which are indubitable. On these foundations, Descartes applies three
levels of skepticism, which in turn, generate three levels at which our thoughts
may be deceived by error. Descartes states quite explicitly in the synopsis,
that we can doubt all things which are material as long as "we have no
foundations for the sciences other than those which we have had up till
now"(synopsis:12). This skepticism also implies that doubt can free us from
prejudices, enabling the mind to escape the deception of the senses, and
possibly discover a truth which is beyond doubt. The first and main deception in

Descartes opinion has evolved from sense perception "What ever I have up
till now accepted as most true I have acquired either from the senses or through
the sense. But from time to time I have found that the senses deceive, and it is
prudent never to trust completely those who have deceived us even
once"(1:18[13]). At the root of our beliefs, Descartes argues, lie the
experiences we gain from our senses, because these are sometimes mistaken, as in
the case of mirages or objects which appear small in the distance, and because
of this he will now forfeit all of his most reliable information . More
importantly it may be to follow in the steps of Plato and require knowledge that
is certain and absolute ( Prado 1992 ). This argument consists of four main
premises: 1. All that he has accepted as true up to this point, he has acquired
by the senses or Cartesian Doubt 3 through the senses; 2. but on occasion these
senses have been deceptive. 3. It is wise not to trust anything that has been
deceiving in the past 4. Therefore, it is possible to be mistaken about
everything. In premise one his beliefs are derived from the senses, such as he
sees that he has a paper in his hand and concludes that it is a paper, and what
is meant by through the senses, is that his beliefs may have been based on
others sense experience. All Descartes requires for the second premise is the
possibility that he may have been deceived, for if he cannot decide which is
wrong, than he must not have any knowledge. This leads to the third premise
where it seems at least reasonable to assume, that if one has been deceived
previously, there is no absolute assurance that it is presently correct.

Therefore, there is a chance of being deceived about everything. But many
critics will argue that several of these false percepts can be corrected by
means of alternative senses, such as he bent stick in water example. Although
our sight may be tricked into thinking that the mirage exists, by using the
sense of touch we can correct this falseness, and uncover what truly exists.

Descartes does retreat, and assess the damage from his first level by saying,
"there are many other beliefs about which doubt is quite impossible, even
though they are derived from the senses-for example, that I am here, sitting by
the fire, wearing a winter dressing gown.." (1:18[12]). Here even he
objects to the validity of his argument, even if he could be deceived about
anything he perceives, this does not mean that he is deceived about everything.

Just because his senses are unreliable at times is not proof enough that
everything in the world is false (Williams 1991). In addition to being
delusional, Descartes believes we can be tricked by madness or insanity. Since
those who are insane may interpret things detached from reality by means of
their senses, " how could it be denied that these hands or this whole body
are mine? Unless perhaps I were to liken myself to madmen, whose brains are so
damaged by the persistent vapours of melancholia" (1:19 [13]), they in fact
believe these percepts to be true. Though Descartes does go on to say "such
people are insane, and I would be thought equally mad if I took anything from
them as a model for myself", and continues by likening the dreams he has to
the experiences a madman faces when awake. From here Descartes makes a stronger
argument for calling into question his common sense beliefs, the possibility
that he