Joshua Rothman in The New Yorker:
I was nineteen, maybe twenty, when I realized I was empty-headed. I was in a college English class, and we were in a sunny seminar room, discussing “For Whom the Bell Tolls,” or possibly “The Waves.” I raised my hand to say something and suddenly realized that I had no idea what I planned to say. For a moment, I panicked. Then the teacher called on me, I opened my mouth, and words emerged. Where had they come from? Evidently, I’d had a thought—that was why I’d raised my hand. But I hadn’t known what the thought would be until I spoke it. How weird was that?
Later, describing the moment to a friend, I recalled how, when I was a kid, my mother had often asked my father, “What are you thinking?” He’d shrug and say, “Nothing”—a response that irritated her to no end. (“How can he be thinking about nothing?” she’d ask me.) I’ve always been on Team Dad; I spend a lot of time thoughtless, just living life. At the same time, whenever I speak, ideas condense out of the mental cloud. It was happening even then, as I talked with my friend: I was articulating thoughts that had been unspecified yet present in my mind. My head isn’t entirely word-free; like many people, I occasionally talk to myself in an inner monologue. (Remember the milk! Ten more reps!) On the whole, though, silence reigns. Blankness, too: I see hardly any visual images, rarely picturing things, people, or places. Thinking happens as a kind of pressure behind my eyes, but I need to talk out loud in order to complete most of my thoughts.