Revenge is an instinctive emotional reaction to being threatened or harmed. When our distant ancestors lived in tribal groups of around 100, in which everyone knew everyone personally and almost all were blood relatives, serious conflicts among members was rare and mild. (How often do people do serious harm to family members even today?)
The next tribe down the river, well those guys were competitors for scarce resources. If they tried to encroach on our hunting grounds or the place in the woods where we gathered our herbs and berries, they were threatening our survival. Unless there had been a plague or famine that wiped out a large segment of both tribes and cooperation for the survival of the species was in order, or unless there were an unusual bounty of food so there was no threat, we had to fight them off.
Injuries would occur during the fighting. This worked against our survival because injured people might die or at least they might not be able to hunt or gather efficiently for a while. They could be permanently injured and become a burden. Our emotional instinct for revenge was well founded. We had to go over to their camp and inflict some injuries on their people, to make the point that it was not in their best interest to encroach on our space again.
Of course there are many versions of this scenario, including those in which the invasion was successful. But in almost all cases, it served our survival instinct to take revenge on those who attacked us.
In a species with language, revenge can be passed down from one generation to the next. "Remember to attack the XYZ clan every couple of years. They killed your grandpa and uncle Thogg and stole some of our food." Eventually the XYZ clan and the ABC clan simply hated each other and no member of either clan could quite remember why, but it was important to exact revenge often enough to refresh the hatred.
You see where I'm going with this, I'm sure. If you don't, then just think about the Middle East. People there are fighting each other over stuff that happened thousands of years ago. Most of them have no conscious understanding of the reasons. They're just doing what their elders have taught them for fifty or a hundred generations.
You're lucky that the other guys weren't there when you came back armed. If you're good enough that you actually got away from them when they had superior weaponry, then when you were evenly matched you might well have inflicted some physical damage on them. Do you really think it would have ended at that?
They would have told their brothers and homies, and a much larger group would have come looking for you. After they beat the crap out of you, your cousins and everybody you know would have gone looking for them. And so on. The size of the group keeps growing, and the most recent recruits don't even quite know what they're fighting for, just something to do with those other guys being really bad assholes that have to be kept in their place.
Does this sound silly? Perhaps it is but it happens every day, right here in America. Street gangs fight over stuff that happened forty years ago, stuff that nobody remembers. The feud between the Hatfields and the McCoys that's been going on for six generations may be a Bible Belt legend, but don't think for a second that there aren't feuds like that going on in the backwoods.
One of the principles of civilization is that justice is dispensed by a dispassionate central authority, not by a bunch of angry citizens who are being temporarily ruled by their feelings rather than their heads.
At the microcosmic level it may actually appear reasonable to hurt or even kill someone who has committed an atrocity like stealing your food or hitting you with a bat in a subway station. (When you get angry the adrenaline and endorphines make you stronger and stupider than normal--even a sensible member of SciForums could kill someone in anger without even meaning to.) But you have to remember that even assholes have people who love them. You are not just hurting the assholes, you're hurting their families, friends, lovers, classmates, teachers, counselors, pastors--everyone who ever tried to raise them and help them is now broken-hearted because they feel it's their own personal fault that the asshole didn't reform.
Some of those people will be so heartbroken that they might lose their sense of rationality and come looking for you. And then your friends, family, and other loved ones will be heartbroken. And some of them might lose their cool and perpetuate the feud.
Okay, perhaps every single one of those people is stronger and more sensible than you and the guy who hurt you. But still, do you want to hurt all those people?
This is the essence of my intractable opposition to capital punishment except in cases where it's the only way to prevent a repeat offense. (We wisely don't trust our justice system to keep its word on "life imprisonment without possibility of parole" and certain categories of offenders like rapists and terrorists have proven to be unreformable.) You might get some twisted satisfaction out of knowing that the person who killed your friend or father is executed. But that's not punishment. He's dead, he's not sitting there saying oh crap I really got punished that time. He's not suffering. The ones who are suffering are his wife and children and parents and boy scout leader. Only the most unrepentant Freudian would suggest that they played a significant part in the crime and deserve that degree of punishment.
Revenge is an atavistic emotion. It is something we have to overcome in order to advance civilization. Again, if you don't believe me just look at the Middle East. To call that a "civilization" is a big joke. It's just a bunch of gangs out gunning for each other because somebody's ancestor did something to somebody else's ancestor that nobody remembers accurately if at all.
