**How optimization took over the world and the urgent case for a new approach** Optimization is the driving principle of our modern world. We now can manufacture, transport, and organize things more cheaply and faster than ever. Optimized models underlie everything from airline schedules to dating site matches. We strive for efficiency in our daily lives, obsessed with productivity and optimal performance. How did a mathematical concept take on such outsize cultural shape? And what is lost when efficiency is gained? * Optimal Illusions* traces the fascinating history of optimization from its roots in America’s founding principles to its modern manifestations, found in colorful stories of oil tycoons, wildlife ecologists, Silicon Valley technologists, lifestyle gurus, sugar beet farmers, and poker players. Optimization is now deeply embedded in the technologies and assumptions that have come to comprise not only our material reality but what we make of it. Coco Krumme’s work in mathematical modeling has made her acutely aware of optimization’s overreach. Streamlined systems are less resilient and more at risk of failure. They limit our options and narrow our perspectives. The malaise of living in an optimized society can feel profoundly inhumane. *Optimal Illusions* exposes the sizable bargains we have made in the name of optimization and asks us to consider what comes next.