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.

When I have a difficult subject before me - when I find the road narrow, and can see no other way of teaching a well established truth except by pleasing one intelligent man and displeasing ten thousand fools - I prefer to address myself to the one man, and to take no notice whatever of the condemnation of the multitude; I prefer to extricate that intelligent man from his embarrassment and show him the cause of his perplexity, so that he may attain perfection and be at peace.

Do not imagine that these most difficult problems can be thoroughly understood by any one of us.

For every force charged by God, may He be exalted, with some business is an angel put in charge.

He, however, who begins with Metaphysics, will not only become confused in matters of religion, but will fall into complete infidelity.

No disease that can be treated by diet should be treated with any other means.

This must be our belief when we have a correct knowledge of our own self, and comprehend the true nature of everything; we must be content, and not trouble our mind with seeking a certain final cause for things that have none, or have no other final cause but their own existence, which depends on the Will of God, or, if you prefer, on the Divine Wisdom.