The Metaphor of the Panopticon
Foucault borrowed the philosopher Bentham’s architectural conception of the "Panopticon" — a central watchtower, with the prisoners in the ring of cells around it unable to know for certain whether they are being watched at any moment, yet forced always to assume they are and so restrain their own behavior — to figure the core logic of the operation of disciplinary power in modern society: truly effective control no longer relies on public violent punishment, but makes the individual internalize the awareness of "being possibly watched at any time," and so achieve self-discipline.