An interface is where a person and a system meet. Because the two parties are rarely equal, that meeting is a negotiation, and the interface is its settlement: it decides what the person is allowed to know, to question, to change, and to refuse.
Beyond usability
This reframes “usability.” Convenience is the settlement’s friendliest face, but ease that removes your ability to say no is not a service — it is a transfer. The two questions that matter for any interface are simple: what can the person see? and what can they do about it? Good interfaces widen both; wasteful ones narrow them while feeling pleasant.
Why it’s decisive now
As systems gain the power to act on our behalf, the interface becomes the only place authority is granted or withdrawn.