Epictetus
Note by J H Fowler on 12. Friendship.

A Greek philosopher who taught the duty of finding happiness in oneself and apart from external circumstances. He was a slave at Rome in the reign of Nero, but afterwards became free. Expelled with other philosophers from Rome by the Emperor Domitian, he taught at Nicopolis in Epirus. There is a translation of his Golden Sayings in the Golden Treasury Series.