The world is in the midst of a transition to a form of global society. Factors such as economic globalization, communications technology, human mobility, cultural influence and environmental change pull towards a unitary system, even as forces act against this connectivity. We live in a unique historical moment at which human activity can irreversibly alter the planet and its capacity to support life. Unprecedented levels of wealth, technology and institutional capacity can forge a just, peaceful and ecologically resilient future. However, the authors argue, social polarization, geo-political...