In the mid-1990s, neuroscientist Marcus Raichle noticed that the resting human brain was not idle but deeply, consistently active — and in recognizing what others had dismissed as noise, he uncovered a network at the center of memory, selfhood, and imagination. The default mode network, consuming a fifth of the body's energy during rest, turns out to be less a background hum than the very architecture of inner life. What science had been subtracting out as irrelevant was, in fact, the subject itself — a reminder that the most consequential discoveries often hide inside our assumptions about wh