Jacobs’ The Death and Life of Great American Cities attacks modern planning by relocating urban order in the ordinary intelligence of streets. Its iconic idea is “eyes on the street”: public safety emerges not from abstract policing or spatial purification, but from dense mixtures of use, informal attention, active frontages, small transactions and temporal continuity. The theoretical contribution is a radical inversion of functionalist urbanism: the sidewalk becomes a complex social organ rather than residual circulation space. Methodologically, Jacobs proceeds through close observation, inductive urban criticism and a dense reading of everyday conditions, refusing both statistical distance and master-plan abstraction. Its conceptual operation is sidewalk ecology: urban vitality is produced by interdependence among strangers, shops, thresholds, dwellings, children, traffic and public trust. The bridge to wider urban theory is decisive because Jacobs turns everyday urban life into a planning epistemology, linking social complexity, economy, safety and morphology.