Wisdom from the Early Stoics, Zeno of Citium 12

According to Hippobotus, he forgathered with Diodorus, with whom he worked hard at dialectic. And when he was already making progress, he would enter Polemo's school: so far from all self-conceit was he. 

In consequence Polemo is said to have addressed him thus: "You slip in, Zeno, by the garden door—I'm quite aware of it—you filch my doctrines and give them a Phoenician make-up." 

A dialectician once showed him seven logical forms concerned with the sophism known as "The Reaper," and Zeno asked him how much he wanted for them. Being told a hundred drachmas, he promptly paid two hundred: to such lengths would he go in his love of learning. 

They say too that he first introduced the word Duty and wrote a treatise on the subject. It is said, moreover, that he corrected Hesiod's lines thus:  

He is best of all men who follows good advice; good too is he who finds out all things for himself. 

[Zeno has reversed Hesiod's order]

—Diogenes Laërtius, 7.25

IMAGE: Polemon, or Polemo, one of Zeno's teachers, as depicted in a Renaissance manuscript