I don't know everything

I had a conversation with Zoo Boy yesterday. It went like this:

ZB: Mommy, are there clouds at night?

me: Mm hmm.

ZB: But I don't see them.

me: It's too dark to see them. But we can tell they are there because when there are clouds at night, we can't see the stars.

ZB: Why not?

me: Because the clouds are closer to us than the stars are, and they hide them.

ZB: How do YOU know?

(The YOU emphasized there, because that's how he always says it. Which leads me to believe that it's less a question of curiosity as it is a "how could an idiot like you possibly know something like that?")

me: Because I've lived a long time and a I know a lot of things.

ZB: Do you know everything?

me: No, I'm quite sure I don't know everything.

ZB: If you lived a really really long time and took all the classes in the world , would you know everything then?

me: No, not even then. It's not possible for anyone to know everything there is to know.

He contemplated this for a minute or two, then tested that theory.

ZB: Does every farm have chickens on it?

me: Um, no, I doubt every farm does. A lot of them do.

ZB: But you don't KNOW that do you?

me: No, you're right, I don't know that.

ZB: (smiling) Oh, so you DON'T know everything.

True enough.