 “Somehow,” Harry thought, “it isn’t quite the same thing.” But he couldn’t figure out why. “I don’t know,” he said finally to Timmy. “The purpose of your stamp club is to exchange stamps. So when you give someone stamps, you’re supposed to give something back. Just like if someone lends me money, I’m supposed to give it back. But if someone pulls a dirty trick on you, should you do the same thing to him? I’m not so sure.”