This book presents the case for Compassionate Reasoning as a moral and psychosocial skill for the positive transformation of individuals and societies. It has been developed from a reservoir of moral philosophical, cultural, and religious wisdom traditions over the centuries, combined with compassion neuroscience, contemporary approaches to conflict resolution, public health methodologies, and positive psychological approaches to social change. There is an urgent need for human civilization to invest in the broad-based cultivation of compassionate thoughts, feelings, and especially habits. This skill is then combined with moral reasoning to move the self and others toward less anger and fear, more joy and care in the pursuit of reasonable policies that build peaceful families, communities, and societies. There are many people who work for the sake of others, and tend to be kinder, more reasonable, more self-controlled, and more goal-oriented to peace. They are united by a set of moral values and the emotional skills to put those values into practice. The aim of this book is to articulate the best combination of those values and skills that lead to personal and communal sustainability, not burnout and self-destruction. The book pivots on the observable difference in the mind—and proven in neuroscience imaging experiments—between destructive empathic distress on the one hand, and on the other, joyful, constructive, compassionate care. Facing existential threats to life on the planet, humans can and must make such skills universally sustainable and ingrained.