This desire for equalization underlies our sense of justice. It’s been codified throughout the ages into rules and laws, such as the Babylonian king Hammurabi’s classic “an eye for an eye, and a tooth for a tooth,” or the biblical Golden Rule, “Do unto others what you would have done unto you.” In evolutionary biology, it’s known as “reciprocal altruism,”11 and in game theory, it’s called a “tit for tat” strategy.12
