Biologist L. Sun examines the innate sense of fairness displayed by human beings in all kinds of societies throughout history. He argues persuasively that it is an emotion and behavior rooted in our DNA, rather than a product of ideology or convention. Citing animal studies that show that even monkeys react negatively to patently unfair treatment, Sun delves into the issue of why this instinct may have evolved with a new biological framework. Specifically, he identifies two selective forces behind the evolution of fairness. One is the need for resolving conflicts of interest in social groups, and the other is a bottom-up drive pushing toward equality in resource sharing in the hierarchies of society.

Turning to the down side of the fairness instinct, the author shows that when it plays too great a role in leveling inequalities, it can have negative repercussions, such as a society where outstanding achievers arouse envy and only mediocrity is condoned. Even worse is the vicious cycle of spite resulting from an injured sense of fairness, which can easily spill over into violence.

Finally, the author considers the role that fairness plays in religion with its promise to ultimately overcome the prejudices and inequality of human society by offering the hope of divine justice.