Expert systems worked. They saved lives, approved loans, configured factories.

They failed because the world isn't a rulebook. Real knowledge, the kind that handles unexpected cases, adapts to new situations, and makes judgment calls, can't be fully written down in advance. Every case outside the rules required a new rule. Every new domain required starting over. The machine knew exactly what it was told, and nothing more.

That limit turned out to be fundamental, not fixable.