Descartes, René. 1596-1650. French mathematician and philosopher.
"Cogito, ergo sum." (I think, therefore I am.)
"Thus what I thought I had seen with my eyes, I actually grasped solely
with the faculty of judgment, which is in my mind."
"Each problem that I solved became a rule which served afterwards to
solve other problems"
"I thought the following four rules would be enough, provided that I
made a firm and constant resolution not to fail even once in the
observance of them.
The first was never to accept anything as true if I had not
evident knowledge of its being so; that is, carefully to avoid
precipitancy and prejudice, and to embrace in my judgment only what
presented itself to my mind so clearly and distinctly that I had no
occasion to doubt it.
The second, to divide each problem I examined into as many parts
as was feasible, and as was requisite for its better solution.
The third, to direct my thoughts in an orderly way; beginning
with the simplest objects, those most apt to be known, and ascending
little by little, in steps as it were, to the knowledge of the most
complex; and establishing an order in thought even when the objects had
no natural priority one to another.
And the last, to make throughout such complete enumerations and
such general surveys that I might be sure of leaving nothing out."
"It is not enough to have a good mind. The main thing is to use it
"These long chains of perfectly simple and easy
by means of which geometers are
accustomed to carry out their most difficult demonstrations
had led me to fancy that everything that can fall under human knowledge
forms a similar sequence; and that so long as we avoid accepting as true
what is not so, and always preserve the right order of deduction of one
thing from another, there can be nothing too remote to be reached in the
end, or to well hidden to be discovered."
Discours de la Méthode. 1637.
hope that posterity will judge me kindly, not only as to the things
which I have explained, but also to those which I have intentionally
omitted so as to leave to others the pleasure of discovery."