Lisa: By your logic I could claim that this rock keeps tigers away. Homer: Oh, how does it work? Lisa: It doesn't work. Homer: Uh-huh. Lisa: It's just a stu

Lisa: By your logic I could claim that this rock keeps tigers away. Homer: Oh, how does it work? Lisa: It doesn't work. Homer: Uh-huh. Lisa: It's just a stupid rock. Homer: Uh-huh. Lisa: But I don't see any tigers around, do you? [Homer thinks of this, then pulls out some money] Homer: Lisa, I want to buy your rock.