Pleasures take to themselves wings and fly away; true knowledge remains forever.

To know that we know what we know, and to know that we do not know what we do not know, that is true knowledge.

Where there is shouting, there is no true knowledge.

To know what you know and what you do not know, that is true knowledge.

Men need knowledge in order to overpower their passions and master their prejudices.

If we will disbelieve everything, because we cannot certainly know all things, we shall do much what as wisely as he who would not use his legs, but sit still and perish, because he had no wings to fly.