Modern urban history makes this conflict legible. Haussmann’s Paris shows the force of autocratic renewal: demolition, infrastructure, hygiene, rent increase, segregation and monumental order appear together, inseparable from the regime that enabled them. Penn Station reveals another condition: when market utility destroys architectural memory, loss can retroactively produce a preservation movement. The struggle between Robert Moses and Jane Jacobs condenses the most contemporary lesson: the growth machine can be interrupted when local knowledge, media action and civic organisation become political force. Urbanism is never only top-down or bottom-up. It is a negotiated, asymmetrical and often violent ecology of powers. Its ethical question is not whether the city changes, but who pays the cost of change, who receives its benefits, and who has the right to speak before the plan becomes irreversible.