The husbandman cannot cultivate every tree, nor can the hunter tame every kind of animal, so both seek means to derive profit according to their several necessities, the one from his barren trees, the other from his wild animals. Sea-water also is undrinkable and brackish, but it feeds fish, and is a sort of vehicle to convey and transport travellers anywhere. The Satyr, when he saw fire for the first time, wished to kiss it and embrace it, but Prometheus warned him,
For fire burns whoever touches it, but it also gives light and warmth, and is an instrument of art to all those who know how to use it.5 Consider also in the case of the enemy, if he is in other respects injurious and intractable, he somehow or other gives us a handle to make use of him by, and so is serviceable. And many things are unpleasant and detestable and antagonistic to those to whom they happen, but you must have noticed that some use even illnesses as a period of rest for the body, and others by excessive toil have strengthened and trained their bodily vigour, and some have made exile and the loss of money a passage to leisure and philosophy, as did Diogenes and Crates. And Zeno, when he heard of the wreck of the ship which contained all his property, said, "Thou hast done well, Fortune, to confine me to my threadbare cloak."6
For as those animals that have the strongest and healthiest stomachs eat and digest serpents and scorpions, and some even feed on stones and shells, which they convert into nourishment by the strength and heat of their stomachs, while fastidious people out of health almost vomit if offered bread and wine, so foolish people spoil even their friendships, while the wise know how to turn to account even their enmities.
§ iii. In the first place then it seems to me that what is most injurious in enmity may become most useful to those that pay attention to it? To what do I refer? Why, to the way in which your enemy ever wide awake