Principle A conviction, distilled from the work.

Know the one-way doors from the two-way

Judgment is mostly telling reversible decisions from irreversible ones, and spending your caution accordingly.

A door you can return through, arrow both ways (top), versus one that closes behind you, arrow once + a wall (bottom, brass).

Most decisions are reversible. You can walk through the door, look around, and walk back out if you were wrong. A few are not: once you are through, the door only opens one way.

The failure is treating the two the same. Teams grind to a halt debating two-way doors as if they were permanent, then wander carelessly through the one-way ones. Judgment is mostly the skill of telling them apart: moving fast and cheap on what you can undo, and slowing down, widening the circle, and buying information on what you cannot.

Jeff Bezos framed this as one-way and two-way doors; the lean tradition calls it deciding at the last responsible moment. The discipline is the same either way. Match the weight of a decision to the cost of being wrong, not to how large it feels in the moment.

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