In the late eighteenth century, Jeremy Bentham sketched a prison he called the Panopticon: cells arranged in a ring around a single watchtower. Its unsettling genius lay in what the prisoners could not know — whether, at any given moment, anyone in the tower was actually looking. Michel Foucault took this design as a model for how modern societies keep people in line. Since the watcher cannot be verified, no guard need lay a hand on anyone; the mere possibility of being seen is enough to secure obedience.

In time the outside eye is taken inward. The inmate, the pupil, the employee starts to watch and correct himself, bending his conduct to the rules without being told. In our own day the arrangement has outgrown walls entirely: our data is gathered without pause and our every move leaves a lasting trace, so that we live inside a Panopticon with no edges. The deepest and most efficient control, the passage suggests, comes not from force steadily applied, but from       ?      .