In the thought-provoking tradition of Steven Pinker’s Enlightenment Now and Yuval Noah Harari’s Homo Deus, a fascinating and reassuring look at the philosophy, psychology, and practice of optimism, and why being optimistic is a moral obligation—even in the face of seemingly insurmountable challenges. Scrolling through our daily newsfeeds we see violence and cruelty, turmoil and injustice, fake news and clickbait, and worsening environmental and social crises—just a few of the dark currents feeding a tidal wave of pessimism. In the face of so many challenges, how can we stay optimistic? And, more important, why should we? In The Bright Side, Sumit Paul-Choudhury answers these pressing questions, arguing that optimism is not only essential for overcoming the challenges we face, but also fundamental to human wellbeing. Drawing on a wide array of evidence—from biology to history, and from economics to meteorology—he delves into the underappreciated roots of optimism, examines its impact on mental health and professional success, and discusses why it has a power that wishful thinking lacks. Additionally, The Bright Side shows how we can apply the principles of optimism to cope with environmental crises, artificial intelligence, and social change. From the polar reaches to the world’s mightiest cities, through inspirational figures including explorers, activists, and scientists, the book illustrates optimism in action. A beacon amid dark times, The Bright Side provides a lens through which we can see the challenges we face more clearly—and it also offers tools for solving them, to create a better future for ourselves and generations to come.