At plausible rates of growth in population and income per capita, world GDP in 2050 could be four times what it is today. This paper considers the benefits this growth can provide, the risks that it presents, and the building blocks required to achieve it. The authors argue that “business as usual” risks unsustainable outcomes. The alternative—responsible growth that sustains environments and supports social development—requires long term thinking if it is to be achieved. Dealing with near-term inequality, improving governance in developing countries, and providing global public goods, particularly vaccine development for tropical diseases and tropical agricultural research, will be key to attaining the prosperous future the authors envision.