<blockquote>18. “The roots of education,” [Aristotle] said, “are bitter, but the fruit is sweet.” Being asked, “What is it that soon grows old?” he answered, “Gratitude.” He was asked to define hope, and he replied, “It is a waking dream.” When Diogenes offered him dried figs, he saw that he had prepared something caustic to say if he did not take them; so he took them and said Diogenes had lost his figs and his jest into the bargain. And on another occasion he took them when they were offered, lifted them up aloft, as you do babies, and returned them with the exclamation, “Great is Diogenes.” Three things he declared to be indispensable for education: natural endowment, study, and constant practice. On hearing that some one abused him, he rejoined, “He may even scourge me so it be in my absence.” Beauty he declared to be a greater recommendation than any letter of introduction. 19. Others attribute this definition to Diogenes; Aristotle, they say, defined good looks as the gift of god, Socrates as a short-lived reign, Plato as natural superiority, Theophrastus as a mute deception, Theocritus as an evil in an ivory setting, Carneades as a monarchy that needs no bodyguard. Being asked how the educated differ from the uneducated, “As much,” he said, “as the living from the dead.” He used to declare education to be an ornament in prosperity and a refuge in adversity. Teachers who educated children deserved, he said, more honour than parents who merely gave them birth; for bare life is furnished by the one, the other ensures a good life. To one who boasted that he belonged to a great city his reply was, “That is not the point to consider, but who it is that is worthy of a great country.”

Source: Lives of the Eminent Philosophers (1925) by Diogenes Laërtius, translated by Robert Drew Hicks </blockquote>