This book uses historical analysis, constitutional economics, and complexity theory to furnish an account of city subsidiarity as a legal, ethical, political, and economic principle. The book contemplates subsidiarity as a constitutional principle, where cities would benefit from much wider local autonomy. Constitutional economics suggests an optimal limit to jurisdictional footprints (territories). This entails preference for political orders where sovereignty is shared between different cities rather states where capital cities dominate. The introduction of city subsidiarity as a constitutional principle holds the key to economic prosperity in a globalizing world. Moreover, insights from complexity theory suggest subsidiarity is the only effective response to the ¿problem of