Insomnia is a gross feeder. It will nourish itself on any kind of thinking, including thinking about not thinking.

Fadiman personifies insomnia as a voracious organism that survives by consuming mental activity. The line captures a familiar paradox: attempts to “force” sleep by monitoring one’s thoughts often backfire, because the very effort becomes more thought—fresh fuel for wakefulness. By including “thinking about not thinking,” he points to the self-referential loop at the heart of anxious sleeplessness, where vigilance about one’s own mind keeps the mind active. The quote implicitly recommends a different strategy: not wrestling with thought, but letting it pass without engagement, breaking the cycle that sustains insomnia.