The author describes how things are getting better and explains why. Prosperity comes from everybody working for everyone else. The habit of exchange and specialization--which started more than 100,000 years ago--has created a collective brain that sets human living standards on a rising trend. The mutual dependence, trust, and sharing that result are causes for hope, not despair. It covers the entire sweep of human history from the Stone Age to the Internet, from the stagnation of the Ming empire to the invention of the steam engine, from the population explosion to the likely consequences of climate change. It ends with a confident assertion that thanks to the ceaseless capacity of the human race for innovative change, and despite inevitable disasters along the way, the twenty-first century will see both human prosperity and natural biodiversity enhanced.