The first duty of man is the seeking after and the investigation of truth.
The roots of knowledge are bitter, but its fruit are sweet.
The foolishness of old age does not characterize all who are old, but only the foolish.
Every one is least known to himself, and it is very difficult for a man to know himself.
Those who do not know history will forever remain children
The pursuit, even of the best things, ought to be calm and tranquil.