Good question. Good answer.

Not long after I walked in from work yesterday, The Boy started shaking his head back and forth.

The Boy: Daddy.
Me: Yes?
The Boy: I can hear my brain move in my head when I do this.
Me: What?
The Boy: I can hear my brain in my head when I move it back and forth.
Me: [Pause] What does it sound like?
The Boy: A rock.

Okay. And then a little later as I'm running the bath and as my wife is negotiating with Q over something, the boy comes in. Quiet, he eventually stops in the middle of pulling off his second sock.

The Boy: Daddy.
Me: Yes?
The Boy: What is thinking?

Now unlike many questions I expect to encounter as a parent (about, e.g., the origin of babies and whatnot), this one I've actually been trained to answer, have actually studied for years, published articles on, and have given talks to learned audiences about with complicated slides. This was my moment. Supposedly.

Me: That's a good question—a really difficult question. I think thinking is a little like asking yourself questions and then answering them to yourself.
The Boy: [skeptical look]
Me: That's how I think about it, anyway.
The Boy: [skeptical look]
Me: ...
The Boy: [skeptical look]
Me: What do you think thinking is?
The Boy: I think with my imagination.
Me: I like that. That's a good way of thinking about it, too.

He's got the making of a philosopher. Unfortunately.

Remember kids: Stay in school. (Just not for too long.)