The document discusses the differences between a "closed city" and an "open city". A closed city is characterized by over-determination through strict rules and fixed building functions that prevent adaptation. An open city follows principles of an open system by exchanging resources and allowing ambiguous boundaries, incomplete building forms, and unsolved development paths. This encourages interaction between communities and more efficient conversion of buildings over time as needs change. The city of the future is envisioned as more open, multi-ethnic, and with a less rigid class structure.