Knowledge is not rules

The knowledge problem ran even deeper.

You ride a bicycle. Try writing down exactly how — not just "balance" and "pedal," but the precise adjustments, the tiny corrections, the feel of the road through the handlebars.

Most of what you know can't be put into words at all. It lives in habit, in muscle memory, in the body's feel for a situation. When researchers sat down with doctors and engineers to extract their knowledge into rules, something essential was always lost in the translation. The rules captured the outline. The judgment that made the expertise real didn't survive the transcription.