A note from Itô
A stop button is not a last resort. It is an admission, made in advance, that conditions can change faster than a plan. The decision to pause should not depend on one person finding the right words at the right moment.
Designing a stop means asking what can go wrong at each layer: data, execution, controls, and the assumptions that tie them together. It means making the safe action clear and technically possible, rather than hoping that a process will hold under pressure.
It also teaches humility. A system that can be paused is a system whose makers accept that they do not have a complete picture. Stopping is not the opposite of discipline. Sometimes it is the clearest expression of it.