Mother Teresa once said, "If I look at the mass, I will never act. If I look at the one, I will." This is the psychological reality of "Compassion Fade" or the "Identifiable Victim Effect." Our brains are wired to feel intense empathy for a single tragedy—a child in a well, a stranded dog—but as the number of victims rises, our emotional engagement paradoxically shuts down. We care less about 100 people than we do about one.

This book explores the evolutionary reasons for this moral bug. We evolved to care for a small tribe, not a statistical dataset. The author explains how charities, news media, and politicians manipulate this bias, and how we can train ourselves to overcome it. By understanding the arithmetic of compassion, we can learn to make decisions based on impact rather than narrative, and ensure that our empathy scales with the magnitude of the suffering.