Jacobs argued, against the planning orthodoxy of her time, that the safest streets were not the streets with the most police but the streets with the most people — different people, present for different reasons, at different times, their ordinary attention to their surroundings producing a distributed, redundant, self-maintaining safety that no formal system could replicate. She called this mechanism eyes on the street. It worked because it was emergent: no single pair of eyes was critical, the coverage was not planned, and the knowledge — who belongs here, who does not, who needs help, who is trouble — circulated through casual contact among the regulars who happened to be present.
Professional quality works through an analogous mechanism. The formal quality systems in a software team — code reviews, automated testing, QA processes — are the police patrols of software quality: necessary, structured, important. But the majority of