Literally "law as retaliation" in the Latin language, lex talionis is the belief that the purpose of the law is to provide retaliation for an offended party. This early belief is reflected in the code of Hammurabi and in the laws of the Old Testament. The most common expression of lex talionis is "an eye for an eye". Legal codes following the principle of lex talionis have one thing in common- proscribed counterpunishment for an offense. In the famous legal code written by Hammurabi, the prinicple of exact reciprocity is very clear. For example, if a person caused the death of another person's child, that person's child would be put to death.

Various ideas regarding the origins of lex talionis exist, but a common and accepted one is that lex talionis developed as early civilizations had an increased population and a less well-established system for retribution of wrongs, feuds and vendettas, threatened social fabric. Despite having been replaced with newer modes of legal theory, lex talionis systems served a critical purpose in the development of social systems- the establishment of a 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.