We play games to learn about the world, to understand our minds and the minds of others, and to practice making predictions about the future. Games are also fun. Here, neuroscientist and physicist Kelly Clancy chronicles the riveting and hidden history of games since the Enlightenment, weaving an unexpected path through military theory, biology, artificial intelligence, neuroscience, cognitive psychology, and the future of democracy. Games, Clancy shows us, have been deeply intertwined with the arc of history. War games shaped the outcomes of real wars in 19th and 20th century Europe. Game theory still underlies basic assumptions in economics, politics, and technology. Now we are designing games that will determine the shape of society and future of democracy. This makes the bold argument that the human fascination with games is the key to understanding our nature.