Diogenes

It takes a wise man to discover a wise man.

When asked what was the proper time for supper: If you are a rich man, whenever you please; and if you are a poor man, whenever you can.

Protagoras asserted that there are two sides to every question, exactly opposite to each other.

Those who have virtue always in their mouths, and neglect it in practice, are like a harp, which emits a sound pleasing to others, while itself is insensible of the music.

When Thales was asked what was difficult, he said, "To know one's self." And what was easy, "To advise another."

Man is the most intelligent of the animals - and the most silly.

The mob is the mother of tyrants.

The sun too penetrates into privies, but is not polluted by them.

To arrive at perfection, a man should have very sincere friends or inveterate enemies; because he would be made sensible of his good or ill conduct, either by the censures of the one or the admonitions of the other.

I am a citizen of the world.