Epictetus

Epictetus (Greek: Ἐπίκτητος, English: Epictetus; 55 CE-125 CE or 130 CE) was a Roman Stoic philosopher who taught that the source of happiness is the mind, not external things. He called for brotherhood and did not write anything himself; his teachings were recorded by his student Arrian. He belonged to the philosophical school founded by Zeno of Citium, who proposed the theory of the cosmic city.

Source: Wikipedia