The last several centuries have each come to have a defining theme: the Age of Enlightenment, the Age of Imperialism, the American Century. We do not know how the 21st will be remembered, but we can say with conviction what its defining goal should be: to grow the circle of opportunity until it reaches all of us, especially those in what is sometimes called the Global South. This task begins, and will be deeply intertwined with, the fight against climate change.