The phrase "an eye for an eye", (עין תחת עין) is a quotation from in which a person who has taken the eye of another in a fight is instructed to give his own eye in compensation. At the root of the non-Biblical form of this principle is that one of the purposes of the law is to provide equitable retaliation for an offended party. It defined and restricted the extent of retaliation. This early belief is reflected in the Code of Hammurabi and in the laws of the Hebrew Bible (e.g., , , ).
Under the right conditions, such as the ability for all actors to participate in an iterative fashion, the "eye for an eye" punishment system has a mathematical basis in the Tit for tat game theory strategy.
The simplest example is the "eye for an eye" principle. In that case, the rule was that punishment must be exactly equal to the crime. Conversely, the twelve tables of Rome merely prescribed particular penalties for particular crimes. The Anglo-Saxon legal code substituted payment of wergild for direct retribution: a particular person's life had a fixed value, derived from his social position; any homicide was compensated by paying the appropriate wergild, regardless of intent. Under the 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 principle is found in Babylonian Law, see Code of Hammurabi. It is surmised that in societies not bound by the rule of law, if a person was hurt, then the injured person (or their relative) would take vengeful retribution on the person who caused the injury. The retribution might be much worse than the crime, perhaps even death. Babylonian law put a limit on such actions, restricting the retribution to be no worse than the crime, as long as victim and offender occupied the same status in society, while punishments were less proportional with disputes between social strata: like blasphemy or laesa maiestatis (against a god, viz., monarch, even today in certain societies), crimes against one's social better were systematically punished as worse.
The Oral Law explains, based upon the biblical verses, that the Bible mandates a sophisticated five-part monetary form of compensation, consisting of payment for "Damages, Pain, Medical Expenses, Incapacitation, and Mental Anguish" — which underlies many modern legal codes. Some rabbinic literature explains, moreover, that the expression, "An eye for an eye, etc." suggests that the perpetrator deserves to lose his own eye, but that biblical law treats him leniently. − Paraphrased from the Union of Orthodox Congregations
However, the Torah also discusses a form of direct reciprocal justice, where the phrase "An eye for an eye, a tooth for a tooth" makes another appearance (). Here, the Torah discusses false witnesses who conspire to testify against another person. The Torah requires the court to "do to him as he had conspired to do to his brother" (). Assuming the fulfillment of certain technical criteria (such as the sentencing of the accused whose punishment was not yet executed), wherever it is possible to punish the conspirators with the exact same punishment through which they had planned to harm their fellow, the court carries out this direct reciprocal justice (including when the punishment constitutes the death penalty). Otherwise, the offenders receive lashes (Makot 1:1; ibid., Bab. Talmud 2a based on critical exegesis of ).
Since there is no form of punishment in the Torah that calls for the maiming of an offender, there is no case where a conspiratorial false witness could possibly be punished by the court injuring to his eye, tooth, hand, or foot. (There is one case where the Torah states "…and you shall cut off her hand…" . The sages of the Talmud understood the literal meaning of this verse as referring to a case where the woman is attacking a man in potentially lethal manner. This verse teaches that, although one must intervene to save the victim, one may not kill a lethal attacker if it is possible to neutralize that attacker through non-lethal injury {Sifrei; Maimonides' Yad, Nezikin, Hil. Rotze'ach u'Sh'mirat Nefesh 1:7}. Regardless, there is no verse that even appears to mandate injury to the eye, tooth, or foot.) Thus, it is impossible to read "an eye for an eye, a tooth for a tooth" literally in the context of a conspiratorial witness. discusses the only form of remotely reciprocal justice not carried out directly by the court, where, under very limited circumstances, someone found guilty of negligent manslaughter may be killed by a relative of the deceased who takes on the role of "redeemer of blood". In such cases, the court requires the guilty party to flee to a designated city of refuge. While the guilty party is there, the "redeemer of blood" may not kill him. If, however, the guilty party illegally forgoes his exile, the "redeemer of blood", as an accessory of the court, may kill the guilty party. Nevertheless, the provision of the "redeemer of blood" does not serve as true reciprocal justice, because the redeemer only acts to penalize a negligent killer who forgoes his exile. Furthermore, intentional killing does not parallel negligent killing and thus cannot serve directly as a reciprocal punishment for manslaughter, but as a penalty for escaping punishment (Makot 7a–13a). (According to traditional Jewish Law, application of these laws requires the presence and maintenance of the biblically designated cities of refuge, as well as a conviction in an eligible court of 23 judges as delineated by the Torah and Talmud. The latter condition is also applicable for any capital punishment. These circumstances have not existed for approximately 2,000 years.)
Based on the literal reading of , Obadiah Shoher argues that "an eye for an eye" punishment only applies for harming the pregnant women. Taken literally, prescribes only reimbursement of medical costs and work income for the harm done to men.
The ideal of vengeance for the sake of assuaging the distress of the victim plays no role in the Torah's conception of court justice, as victims are cautioned against even hating or bearing a grudge against those who have harmed them. The Torah makes no distinction between whether the potential object of hatred or a grudge has been brought to justice, and all people are taught to love their fellow ().
You have heard that it was said, "An eye for an eye and a tooth for a tooth". But I say to you, do not resist an evildoer. If anyone strikes you on the right cheek, turn to him the other also. (NRSV)
The passage continues with the importance of showing forgiveness to enemies and those who harm you. This saying of Jesus is frequently interpreted as criticism of the Hebrew Bible teaching, and often taken as implying that "an eye for an eye" encourages excessive vengeance rather than an attempting to limit it.
It was one of the points of 'fulfilment or destruction' of the Hebrew law which the Church father St. Augustine already discussed in his Contra Faustum, Book XIX.
The opinion that seems to prevail among Christian theologians is that such an interpretation is a misunderstanding of this section of Matthew. But scholars of Christianity have found particular pride in this commandment and others from the Sermon on the Mount, as in badges of distinction for the religion; and Leo Tolstoy went so far as to keep only the Gospel and especially this part of it, and throw the rest of the Bible out.
In Islam the Quran permits exact and equivalent retribution. The Quran, however, softens the law of an eye for an eye by urging mankind to accept less compensation than that inflicted upon him or her by a Muslim, or to forgive altogether. In other words, Islam does not deny Muslims the ability to seek retaliation in the equal measure. But it does, however promote forgiveness and the acceptance of blood money not as a mandatory requisite, but rather as a good deed that will be eventually rewarded (Quran 5:45).
For example the "correctional" prison system (first instituted in the USA in the early 20th century) is based on the idea that the purpose of law enforcement is to correct the deviant nature of criminals by compelling them to reflect and regret their crimes during a lengthy incarceration; another alternative, the reformatory, was invented to "reform", i.e. re-educate, young offenders etcetera.—
Even though it may be hard to do in practice, certain belief systems (such as Christianity) teach individuals to forgive those who wrong them, rather than seek retribution for a wrong. Other belief systems adhere to similar concepts, such as the Taoist wu wei which encourages a wronged individual to simply accept the infraction and to take the least "resistive" action to correct it, if any action need to be taken at all. Buddhism stresses the weight of karma: one can take retributive action, but that retributive action is not without its consequences, and living on a finite planet guarantees that the suffering incurred by a retributive action will return to the individual who was wronged (as well as the one who did the wrong-doing). Some subscribe to the Golden Rule of ethics rather than any law of retaliation.
It can also be seen as an extension of the informal logical fallacy, two wrongs make a right.