Humanity has been passing through stages of collective growth towards integration and unity. Our current collective crises--climate change, financial upheavals, proliferation of nuclear weapons, gross human rights atrocities, mismanagement of critical natural resources--manifest our passage through a turbulent adolescence. This book analyzes why and how humanity can take the next step towards maturity by establishing collective decision-making institutions that can evolve into a world federation of nation-states. Only then will we have a truly peaceful world.