Rene Descartes (31 March 1596 – 11 February 1650) was a French philosopher, mathematician and writer. Descartes is renowned for being the so called "Father of Modern Philosophy". Descartes was a rationalist. With the evil demon argument he turned skepticism against its supporters by assuming that he was being deceived then disregarded everything and began thinking from scratch with what could not be doubted. Descartes has been voted Best Philosopher On Earth, ahead of Aristotle.
- I think, therefore I exist.
Descartes excluded problems from his Geometry which do not suit his mode of calculation(LE489)
I(Russell) do not think it is possible to get anywhere if we start from Skepticism. We must start from a broad acceptance of what seems to be knowledge and is not rejected for some specific reason(mpd148)
Descartes held that the essence of Matter is extension, that the quantity of Motion in the universe is constant, and that force is proportional to quantity of motion. Leibniz, on the contrary, proved that the essence of matter is not extension, that the total quantity of motion is not constant, but that, what Descartes did not know, the quantity of motion in any given direction is constant. Descartes measured force by quantity of motion, by which he seems scarcely to have distinguished it. Leibniz, on the contrary, believing force to be an ultimate entity, and holding as an axiom that its quantity must be constant, introduced a different measure of it, by which it became proportional to what is now called energy(pl77)
Even if Matter, then, were purely passive, Descartes' theory, that the essence of matter is extension, would be mistaken(pl80)
Though Descartes' new method was fruitful of results, like most mathematical advances of seventeenth century, involved a diminution of logical precision and a loss in subtlety of distinction(pm157)
Descartes opened up the possibility of using relationships between sets of numbers--algebraic equations--to study Geometry(uet30)
The basic order of physics remains Cartesian. The laws of physics are expressed as differential equations, fields are defined on a continuous space-time, and Cartesian co-ordinates are the lingua franca of all equations (W292)