This book offers a new standpoint to understanding tolerance to human diversity by approaching it from the perspectives of cognitive, developmental and prosocial psychology. Emphasising the positive aspects of social perception and behaviour, it invites readers to re-consider tolerance not simply as the opposite of prejudice, but as something that can in fact coexist with prejudice and intolerance. Drawing on original empirical research conducted with children, adolescents and young adults, the book maps the response patterns for tolerant judgement and justification, including psycho-developmental factors. It explains how tolerance regarding differences of colour, creed and culture is based on underlying beliefs that guide the reasoning process to support judgements about human diversity. Showcasing emerging theory and a new methodology of data collection that goes beyond common approaches, this book outlines a unique potential developmental trajectory for tolerance to human diversity based on fairness, empathy and reason. The book challenges students, researchers and general readers across the fields of psychology, human ethics and moral philosophy with its new insights into the character of prosocial beliefs.