To fight fire with fire
To fight fire with fire. 要是从字面来解释，那就是：用火来攻火，这当然是不可能的。
实际上，to fight fire with fire就是用你对立面对你用的手法来对待他。也可以说是以其人之道还其人之身。
下面是一个例子，这是一个参加竞选的政客在说话。
例句3: I had hoped this would be a clean campaign. But if my opponent wants to play dirty and talk about my personal life, I have no choice but to fight fire with fire and talk about some personal things we've found out about him.
这个候选人说：我原先希望这次选举是光明正大的。但是，要是我的对手要耍下流手段，谈论有关我私生活的事，那我就别无选择，只好以其人之道还其人之身了，把我们发现有关他私生活的事也公布于众。
下面这个例子是讲一对夫妇。一开始的时候，那个丈夫在外面有外遇。后来，太太也决定用同样的方法来治她的丈夫。下面是他们的一位好朋友在说话。
例句4: Jack and Joan have been my friends for over ten years. I felt bad for Joan when Jack started to have an affair last year. But Joan's decision to fight fire with fire by having an affair herself made things much worse.
这个朋友说：我跟杰克和琼已经是十几年的朋友了。杰克去年开始在外面有外遇。我为琼感到很难受。但是，琼决定自己也去找一个男朋友，用以牙还牙的方式来对待杰克。这可是把事情弄得越来越糟。