Never trust anything that can think for itself if you can't see where it keeps its brain.

The line is spoken by Arthur Weasley in J. K. Rowling’s Harry Potter series, during the events of Harry’s second year at Hogwarts. It appears in the context of the mystery surrounding Tom Riddle’s diary—an enchanted object that seems to “think” and communicate independently, drawing Harry into its memories and ultimately serving as a conduit for dark magic. Mr. Weasley’s remark reflects the Ministry’s and his own professional concern with bewitched artifacts and the dangers of magical objects whose workings are hidden from their users. The warning also resonates with the book’s broader anxiety about manipulation through seemingly benign tools.

On its surface, the quote is a wry, practical warning: be suspicious of any object that displays intelligence when you cannot inspect the mechanism behind it. In the wizarding world, “where it keeps its brain” literalizes the idea of understanding how something works before trusting it. More broadly, it captures a skepticism toward opaque systems—whether magical, technological, or bureaucratic—that can influence a person while concealing their motives and inner logic. In Chamber of Secrets, the diary’s friendly responsiveness masks coercion and possession, making the line a compact statement about the risks of delegating judgment to an unseen intelligence.