The motivating idea of a Universal Basic Income (UBI) is radically simple: give people cash and let them do whatever they want with it. But does this simple idea have the potential to radically transform our society? This book provides the average citizen with all the information they need to understand current debates about the UBI. It recounts the history of the idea, from its origins in the writings of eighteenth century radical intellectuals to contemporary discussions centered on unemployment caused by technological advances such as artificial intelligence. It discusses current pilot programs in the United States and around the world, including how much (or little) we can learn from such experiments about how a large-scale UBI would fare in the real world. It explores both the promises and pitfalls of a UBI, taking seriously the arguments of both supporters and detractors. How much would a UBI cost? Who would be eligible to receive it? Would it discourage work? Would people squander it on drugs and alcohol? Would it contribute to inflation? And how is it different from existing social welfare programs? This book provides an objective, expert guide to these questions and more, and is essential for anyone seeking to understand what could be the twenty-first century's most important public policy debate.