I forgot exactly when this happened, but it was quite a while ago, so I'm guessing F1-1 was about 5, maybe 6 years old. He started a conversation about god. He wondered why people believe in god. So I returned the question:
"Yes, F1-1. Why *do* people believe in god?"
He looked at me with a blank expression for a few moments before he responded, very sure of himself:
"Because some houses have flat roofs on them."
Several moments of silence.
Then I said: "You know, that is as good a reason as any other."
It still is the best I've come across so far.