Climate change is an ethical failure. Floods, fires, droughts, and extreme weather caused by climate change are already killing people and ruining lives on a massive scale. These avoidable impacts hurt the most vulnerable among us first, and worst. Why have we failed to prevent climate change? How can we mobilise to do better politically, socially, and economically? Where does the greatest responsibility for action lie? In this book, Catriona McKinnon unravels the vital contributions made by engaged political theory to urgent climate challenges left unmet by a lack of political will. These challenges, and our political inertia, cannot be tackled without addressing questions of responsibility, collective duty, fairness, harm, techno-optimism, the value of nature, and the future of humanity. McKinnon’s philosophical analysis is interwoven with discussion of the latest climate science, current politics and policies, and emerging technologies, in order to show that we will not find acceptable routes out of the climate crisis without the compass of political theory.