Last night Thea and I were lying in bed recapping the day, as we do every other night. I was explaining why her dad and I wouldn't let her have only potato chips and donuts for lunch. I said that as her parents, we're supposed to keep her from doing what she wants if we know it'll hurt her or make her sick. Then I said, "But you know what's funny? When you're a grown-up, you can eat only potato chips and donuts for lunch if you want, but when you're a grown-up, you still won't do it."
Thea: When I'm a grown-up? I won't want to have only potato chips and donuts for lunch?
Me: Well, you might still want to, but you probably won't do it because you'd know it would make you sick.
Thea: When I'm a grown-up, will I drive a car and have a job and make my own lunch?
Thea: And my lunch won't be just potato chips and donuts, even though no one will tell me I have to have something else?
Thea: [Extended pause while she contemplates....] Are you just teasing me?
Even to me, it does sound rather implausible.