Conversation with Xander

Last night on the way to a meeting at church, Xander & I were talking about his science assignment, which was to think about different parts of plants that we can eat, and I mentioned leaves and how we eat the leaves of herbs like Rosemary and Thyme...

X: Thyme?! What's that?
A: It's a plant. It's spelled T-H-Y-M-E
X: Never heard of it.
A: Just because you've never heard of it doesn't mean it doesn't exist. (this is a point I have to make with him frequently)
X: I don't believe it's a real word.
A: Well it is.
X: Look. I've been learning all kinds of new words in 2nd grade, and I never learned that one, so I don't think it's a word.
A: OK...
X: I mean, I know we walk by faith and not by sight...
A: GOOD APPLICATION, XANDER!
X: But I still don't believe it's a word.

Where does he get this constant need to be right? (Answer: from his dad)