The Age of Why

Me: Rivers, you need to pick up your books.
Rivers: Why?
Me: Because your room is messy.
Rivers: Why?
Me: Because you made a mess and mommy wants you to pick it up.
Rivers: Why?
Me: (somewhat smiling by this point) Because Mommy said so.
Rivers: (laughing) Why?
Me: Because!!!
Rivers: (laughing) Mommy you teasing me!
Me: No I'm not teasing you.
Rivers: (laughing harder) You are!