Born: 31 March 1596 in La Haye (now Descartes),Touraine, France
Died: 11 Feb 1650 in Stockholm, Sweden
"I concluded that I might take as a general rule the principle
that all things which we very clearly and obviously conceive are
true: only observing, however, that there is some difficulty in
rightly determining the objects which we distinctly conceive.
Discours de la Méthode." 1637.
Descartes, as a result of the principles already established in
his method, had first of all to seek out a solid starting point
(a clear and distinct concrete idea), and from this opens his
deductive process. To arrive at this solid starting point, he begins
with methodical doubt, that is, a doubt which will be the means
of arriving at certitude. This differs from the systematic doubt
of the Skeptics, who doubt in order to remain in doubt.
I can doubt all the impressions that exist within my knowing faculties,
whether they be those impressions which come to me through the senses
or through the intellect. Indeed, I may doubt even mathematical
truths, in so far as it could be that the human intelligence is
under the influence of a malignant genius which takes sport in making
what is objectively irrational appear to me as rational.
Doubt is thus carried to its extreme form. But notwithstanding
this fact, doubt causes to rise in me the most luminous and indisputable
certainty. Even presupposing that the entire content of my thought
is false, the incontestable truth is that I think: one cannot doubt
without thinking; and if I think, I exist: "Cogito ergo sum."
It is to be observed that for Descartes the validity of "Cogito
ergo sum" rests in this, that the doubt presents intuitively
to the mind the subject who doubts, that is, the thinking substance.
In this, Cartesian doubt differs from that of St. Augustine ("Si
fallor, sum"), which embodies a truth sufficiently strong to
overcome the position of Skepticism. In Descartes, "Cogito
ergo sum" is assumed, not only in order to overcome the Skeptic
position but as a foundation for the primary reality (the existence
of the "res cogitans"), from which the way to further
research is to be taken.
This is the point which distinguishes the classic realistic philosophy
from Cartesian and modern philosophy. With Descartes, philosophy
ceases to be the science of being, and becomes the science of thought
(epistemology). Whereas, at first, being conditioned thought, now
it is thought that conditions being. This principle, more or less
realized by the philosophers immediately following Descartes, was
to reach its full consciousness in Kant and modern Idealism.
ideas do not come from experience, but the intellect finds them
within itself. Descartes declares that only
these ideas are valid in the field of reality. Thus the concreteness
(or the objective validity) of an idea is dependent upon its own
clearness and distinction.