Homer: The Bear Patrol really seems to be working.
Lisa: Why do you say that, Dad?
Homer: We haven't had a bear attack since they started patrolling.
Lisa: That's specious reasoning, dad.
Homer: Why thank you, Lisa.
Lisa: By that rationale, I could claim that this rock keeps tigers away.
Homer: Explain.
Lisa: Well, you don't see any tigers, do you?
(Long pause)
Homer: Lisa, I would like to buy your rock.