All teaching and all intellectual learning come about from already existing knowledge.

So virtue is a purposive disposition, lying in a mean that is relative to us and determined by a rational principle, and by that which a prudent man would use to determine it. It is a mean between two kinds of vice, one of excess and the other of deficiency.

Quid quid movetur ab alio movetur"(nothing moves without having been moved).

For as the eyes of bats are to the blaze of day, so is the reason in our soul to the things which are by nature most evident of all.

For what one has to learn to do, we learn by doing.

It is absurd to hold that a man ought to be ashamed of being unable to defend himself with his limbs, but not of being unable to defend himself with speech and reason, when the use of rational speech is more distinctive of a human being than the use of his limbs.

There is more both of beauty and of raison d'etre in the works of nature- than in those of art.