a sect of philosophers, who adhere to the system of Des Cartes, and founded on the two following principles; the one metaphysical, the other physical; the metaphysical one is, I think, therefore I am; the physical principal 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 world is absolutely full: where space is precluded by this principle; ciple, in regard, extension being implied in the idea of space, matter is so too.

Upon these principles, the Cartesians explain mechanically, and according to the laws of motion, how the world was formed, and whence the present appearances of nature do rise. They suppose, that matter was created of an indefinite extension, and divided into little square masses, full of angles; that the Creator impressed two motions on this matter; one whereby each part revolved round its centre, another whereby an assemblage, or system, turned round a common centre; whence arose as many different vortices as there were different masses of matter, thus moving round common centres.

The consequences of this hypothesis, according to the Cartesians, will be, that the parts of matter in each vortex could not revolve among each other, without having their angles gradually broken, and that this continual friction of parts and angles produced three elements; the first, an infinitely fine dust, formed of the angles broken off; the second, the spheres remaining, after all the angular irregularities are thus removed; these two make the matter of Des Cartes's first and second element; and those particles not yet rendered smooth and spherical, and which still retain some of their angles, make the third element.

Now, according to the laws of motion, the subtlest element must take up the centre of each system, being that which constitutes the sun, the fixed stars above, and the fire below; the second element, composed of spheres, makes the atmosphere, and all the matter between the earth and the fixed stars, in such a manner as that the largest spheres are always next the circumference of the vortex or system, and the smallest next its centre; the third element, or the hooked particles, is the matter that composes the earth, all terrestrial bodies, comets, spots in the sun, &c. Though both philosophers and divines have a just plea against this romantic system, yet it must be owned, that Des Cartes, by introducing geometry into physics, and accounting for natural phenomena by the laws of mechanics, did infinite service to philosophy.