There is simply no reasoning with a 3-year old, example given:

M: “Will, why are you biting your nails?”

W: “I had to peel back the skin so that… so that… the caterpillar wouldn’t know that I’m in The Incredible Movie.”

M: (repeating) “Help me understand you. You are biting your nails so that a caterpillar wouldn’t know you are in The Incredibles movie?”

W: “No. Uh-huh. I peeled back the skin so that I could be super-fast!”

M: “Hold that thought. I need a piece of a paper to write this down.”