The Tacit Dimension
Michael Polanyi, 1966
A short book with a long shadow. Its central claim — “we know more than we can tell” — is almost a cliché now, which means it’s usually quoted without being understood.
What Polanyi Means
The argument isn’t that some things are hard to articulate. It’s that all knowing involves a tacit dimension — a layer of subsidiary awareness that we rely on but can’t fully attend to. When a blind person feels the path through a stick or probe, they are attending from the instrument to what its tip touches. The instrument has become transparent. That transparency is tacit knowledge.
This from-to structure appears everywhere. A reader attends from the shapes of letters to the meaning of words. A carpenter attends from the feel of the plane to the surface being worked. A diagnostician attends from a constellation of symptoms to the disease. In each case, the subsidiary layer can be noticed — but noticing it disrupts the focal awareness. You stop reading and see letters; you stop planing and see your hands.
Why You Can’t Just Describe It
Polanyi’s own example, from Personal Knowledge (1958), is the cyclist. A rider keeps balance by steering into the direction of a fall, with a curve whose radius is proportional to the square of the speed divided by the angle of imbalance. Hardly any cyclist knows this rule, and knowing it wouldn’t help anyone ride.
The point is serious. The description is true — that is what happens when someone rides a bicycle — but following the description doesn’t produce riding. The knowledge has to be acquired through a different process: guided practice, repeated failure, gradual adjustment. You acquire it in your body before you can name it.
This matters enormously for what AI systems can and can’t do. Large language models are explicit-knowledge engines. They can generate descriptions of how to do things. The descriptions may be accurate. They still can’t substitute for practice in a domain where tacit knowledge dominates.
Connoisseurship and Personal Knowledge
Polanyi’s other major claim is that knowing always involves commitment — a personal stake in the truth being known. Science presents itself as impersonal, but the scientist’s judgment about which anomalies to pursue, which colleagues to trust, which experimental designs make sense — all of this involves personal knowledge that can’t be eliminated without eliminating science itself.
This was a heretical claim when he first made it in Personal Knowledge (1958). It still makes some people uncomfortable. But it squares with what we observe: expertise looks like objectivity from the outside and feels like judgment from the inside.
Connections
- Michael Polanyi — this is his central argument
- embodied-knowledge — the concept this work grounds
- Matthew Crawford — shop class as tacit knowledge in practice
- John Dewey — knowledge through experience; parallel tradition
- Masanobu Fukuoka — decades of observation as tacit agricultural knowledge
- natural-farming — a tradition built on accumulated tacit knowledge
- experience-and-education — Dewey on learning by doing