善用对手。处事如同操刀——抓刀刃会伤手，抓刀柄则可防身。对付敌人更需奉行这一原则。明智之人在对手身上发现的用处比蠢人在朋友身上发现的用处还要多。恶意常常可以激励我们克服本来不愿面对的重重困难，大多数人成就其伟业，都应归功于自己的对手。比憎恶更危险的是谄媚，别人的谄媚掩盖了你的缺点，而别人的憎恶则促使你消除瑕疵。智者把别人的恶意视为一面比善意更真实的镜子，以减少或改正有关缺陷。每个人与对手或敌人比邻而居时，都会变得十分小心。
make use of your enemies. you should learn to seize things not by the blade, which cuts, but by the handle, which saves you from harm: especially is this the rule with the doings of your enemies. a wise man gets more use from his enemies than a fool from his friends. their ill-will often levels mountains of difficulties which one would otherwise not face. many have had their greatness made for them by their enemies. flattery is more dangerous than hatred, because it covers the stains which the other causes to be wiped out. the wise will turn ill-will into a mirror more faithful than that of kindness, and remove or improve the faults referred to. caution thrives well when rivalry and ill-will are next-door neighbours.
