a sect of philosophers, who adhered to the system of Des Cartes, founded on the two following principles, the one metaphysical, the other physical. The metaphysical one is, I think, therefore I am; the physical principle is, that nothing exists but substance. Substance he makes of two kinds; the one a substance that thinks, the other a substance extended; whence actual thought, and actual extension, are the essence of substance.

The essence of matter being thus fixed in extension, the Cartesians conclude that there is no vacuum nor any possibility thereof in nature; but that the universe is absolutely full: mere space is excluded by this principle; because extension being implied in the idea of space, matter is so too. Upon these principles the Cartesians explained mechanically how the world was formed, and how the present celestial phenomena came to take place. See Astronomy Index.