Black Box
Etymology
Engineering slang from the World War II era for a device analyzed purely by what goes in and what comes out, its internals sealed or unknown. "Black" carries the sense of opaque. The term now spans any system whose inner logic we can’t inspect, and features heavily in debates over inscrutable AI.
noun phrase · /blak boks/
A system understood only by its inputs and outputs, with its inner workings hidden or unknowable.
What it names
A tool for reasoning about anything opaque — an algorithm, a bureaucracy, a market, another mind — where you can study behavior at the edges without seeing the mechanism inside.
Example
The recommendation engine is a black box — we can see what it surfaces, not why.
Related idea
The direct opposite of legibility: a black box resists being read from outside, whereas legibility is the quality of a system made transparent and knowable.