The past is certain, the future obscure.

The most difficult thing in life is to know yourself.

Know thyself.

A multitude of words is no proof of a prudent mind.

There are three attributes for which I am grateful to Fortune: that I was born, first, human and not animal; second, man and not woman; and third, Greek and not barbarian.

God is the most ancient of all things, for he had no birth.