DL 6.30 · Diogenes
And he said he marvelled that before we buy a jar or dish we try whether it rings true, but if it is a man are content merely to look at him. To Xeniades who purchased him he said, "You must obey me, although I am a slave; for, if a physician or a steersman were in slavery, he would be obeyed." Eubulus in his book entitled The Sale of Diogenes tells us that this was how he trained the sons of Xeniades. After their other studies he taught them to ride, to shoot with the bow, to sling stones and to hurl javelins. Later, when they reached the wrestling-school, he would not permit the master to give them full athletic training, but only so much as to heighten their colour and keep them in good condition.