For the elements have the property of moving back to their place in a straight line, but they have no properties which would cause them to remain where they are, or to move otherwise than in a straight line. The rectilinear motions of these four elements when returning to their original place are of two kinds, either centrifugal, viz., the motion of the air and the fire; or centripedal, viz., the motion of the earth, and the water; and when the elements have reached their original place, they remain at rest.

Let nothing which can be treated by diet be treated by other means.

How individuals of the same species surpass each other in these sensations and in other bodily faculties is universally known, but there is a limit to them, and their power cannot extend to every distance or to every degree.

Truth does not become more true by virtue of the fact that the entire world agrees with it, nor less so even if the whole world disagrees with it.

A truth does not become greater by repetition.

The more we desire for that which is superfluous, the more we meet with difficulties; our strength and possessions are spent in unnecessary things, and are wanting when required for that which is necessary.

Astrology is a disease, not a science... It is a tree under the shadow of which all sorts of superstitions thrive. ... Only fools and charlatans lend value to it.