Educating the mind without educating the heart is no education at all. - Aristotle
It is better to remain silent at the risk of being thought a fool, than to talk and remove all doubt of it.
One must know oneself. Even if it does not help in finding truth, at least it helps in running one's life, and nothing is more proper. - Blaise Pascal
Wise men talk because they have something to say; Fools, because they have to say something. - Plato