This phrase describes the law of retaliation (lex talionis) in that the person who causes another person to suffer should suffer in an equal amount.
It originated in the Code of Hammurabi, King of Babylon, 1792-1750 BCE. The code survives today in the Akkadian language, and the phrase was used in the King James Bible: “…it hath been said, An eye for an eye, and a tooth for a tooth…” In Hammurabi’s code, the principle is of exact reciprocity. For example, if a person caused the death of another person, the killer would be put to death.
In some interpretations, the injured party is the one inflicting such punishment. In softer interpretations, it means the victim receives the estimated value of the injury in compensation. The intent behind the principle was to restrict compensation to the value of the loss, and thus prevent the feuds and vendettas that threatened social life.
Though lex talionis systems have been replaced by newer legal theory, they served a critical purpose in the development of social systems, the establishment of a governing body whose purpose was to enact the retaliation and ensure that this was the only punishment. This body was the state in one of its earliest forms.
Roman law moved toward monetary compensation as a substitute for vengeance. In cases of assault, fixed penalties were set for various injuries, although talio was still permitted if one person broke another’s limb.
The ideal of vengeance plays no role in the Torah’s conception of court justice, as victims are cautioned against hating or bearing a grudge against those who have harmed them. The Whether or not the guilty party has been brought to justice, all people are taught to love their fellow Israelites.
Under British Common Law, successful plaintiffs were entitled to repayment equal to their loss (in monetary terms). In the modern tort law system, this has been extended to translate non-economic losses into money as well.
The King of Babylon obviously knew what seemed fair. Today, we often apply his code to everyday life, both as children and as adults. Of course, some people say revenge is bad, but there’s immense satisfaction in smacking back a person who has smacked you.
Taking such revenge is one of the basic seven plots used in fiction. I am reminded of a book titled Not a Penny More, Not a Penny Less by Jeffrey Archer, which I thoroughly enjoyed. The protagonists had been scammed for hundreds of thousands of dollars and they recovered, by devious methods, the exact amount taken from them.