*Theoretical computer scientist is at an interview.*

Interviewer: “Imagine that you are walking down a road and see a house on fire. What do you do?”

CS Guy: “I dial the police and tell them that the house is on fire.”

Interviewer: “Good. Now, imagine that you are walking down the same road, and you see that the same house is not on fire. What do you do?”

CS Guy: *Ponders for a little while.* “I put the house on fire, thus reducing it to a problem I’ve solved before.”