Prevention is an immoral reason for punishing criminals. It boils down to “You don’t know whose blood is redder,” or exemplary punishment. Essentially, the government punishes one person to deter or save another. In such a scenario, some criminals suffer punishment for what other would-be criminals might do. Going down this road, the government might as well take hostages from among gang members and execute them if any crime is committed in the vicinity.
The government’s concern with preventing crimes should logically lead to prohibition of crime-inducing circumstances: people must not be allowed to go out at night, poor neighborhoods must be razed, and nightclubs closed. The absurdity of such logical conclusions shows that punishment is not about prevention.

Some argue that punishment, especially capital punishment, has no deterrent effect. Let us consider the opposite possibility: suppose punishment actually encourages more crime, perhaps in protest. Would that be a reason to forfeit punishments? Clearly, punishments have nothing to do with deterrence. Punishment is only about retribution.

The above case is far from theoretical, but very common in foreign relations. It has long been argued that Israeli and American reprisals against terrorist-harboring states do not eradicate terrorism, but cause resentment and so increase the enlistment of people into the ranks of terrorists. But it is not an acceptable policy to swallow the terrorist acts and refrain from punishing the offending nations.

Fringe cases exist. Sometimes, when retaliation cannot force the offender to change his ways and might, on the contrary, provoke him, it might well be advisable to hold off the retaliation for a while to see whether he might cease the aggression. In retrospect, British were wrong to bomb German cities in response to the first German bombardment of London―which, as we know now, was done by mistake.

Modern societies are ill-equipped to condemn the supposed immorality of retribution. In an important sense, they are more brutal than the ancient Jewish society. Consider the common law that allows employers to be punished for the harm done by their employees, even though the employers acted in good faith. By enacting such laws, states transfer their security responsibilities onto employers. The state is under no illusion that employers can thoroughly monitor their workforce. The punishment of employers neither deters them from hiring bad employees, nor prevents those employees from committing crimes. If anything, the law taxes an innocent person (employer) to compensate the victim. In Jewish law, a master is responsible for his slaves’ actions, but the presumption is that slaves are merely instruments under full control of their master.

Another example is parents’ responsibility for the harm inflicted by their children. Jewish law is explicit: parents are not responsible for their children. This is the opposite of a master-slave relationship: children are not their parents’ tools, but from the youngest age are fully responsible for their own actions. Rabbis mitigated that responsibility with low bar mitzvah age, but that innovation is not rooted in the Torah. It is absurd to imagine that children younger than 13 do not understand that theft or murder is a crime. According to this silly modern doctrine of infantilism, Israel cannot prosecute Palestinian children who throw firebombs at Jews.

If parents are responsible for their children, and employers for their employees, though they cannot control them, then nations are all the more responsible for their terrorists. Just as punishing parents and employers does not prevent misbehavior by their dependents, so the punishment of enemy nations need not prevent terrorism. The Torah arrives at a similar conclusion from another angle, namely that nations are treated as a whole without singling out individual (terrorist) members. We were commanded to exterminate Amalek for the actions of its long-gone ancestors. In foreign relations, punishment is mainly about vengeance.

revenge is moral