Scientist Allen Hammond imaginatively probes the consequences of present social, economic, and environmental trends to construct three possible worlds that could await us in the twenty-first century: Market World, in which economic and human progress is driven by the liberating power of free markets and human initiative; Fortress World, in which unattended social and environmental problems diminish progress, dooming hundreds of millions of humans to lives of rising conflict and violence; and Transformed World, in which human ingenuity and compassion succeed in offering a better life, not just a wealthier one, and in seeking to extend those benefits to all of humanity.