Back in the 1970s, the National Film Board of Canada created a series of vignettes that showcased interesting aspects of Canadian culture and history. In one of these, aptly entitled 'Spence's Republic', Thomas Spence gathers the community together in order to create the Republic of Manitoba. He then names himself President of the new republic. The local shoemaker, a man named McPherson, eventually accuses President Spence of using tax money to purchase liqueur for himself and his friends. In retaliation, President Spence orders McPherson's arrest, and at the trial attempts to act as both judge and accuser.
The vignette ends with President Spence's 'historic words'. If you really want to know what they were, you will have to watch the video below. Since they are important to the topic at hand, I suggest you do so.
When human beings gather together as a community, they enact something known of as a 'social contract'. That is, they agree to a set of rules and regulations that everyone needs to follow in order for the community to thrive. They also agree on what the punishment for failing to adhere to the social contract is, and how guilt, innocence, and judgement are to be decided and enacted.
Without these basic rules, civil society will collapse. But, before you start clapping your hands and saying, 'Oh goody....anarchy!', you had better realize that the end result will not be anarchy. It will be lawlessness. If you suddenly become free to rob the liqueur store, it means that someone else is also free to rob you of the liqueur you just stole, and put a bullet in your head while they are at it.
In other words, things quickly spiral out of control, with no one being held accountable for their actions.
The same is true when people decide to enact 'vigilante justice'. The vigilante is someone who feels that justice has to be served, and it has to be served according to their rules, and according to their idea of punishment. Just like President Spence above, they take it upon themselves to act as both judge and accuser. The problem with that is that no independent inquiry has been made into the allegations, and the community as a whole has not agreed upon the punishment for the crime that may have been committed. Without the authority of the community behind him/her, the vigilante's actions have no authority, and constitute a crime in and of themselves.
Let us use the example of someone accidentally killing another person's relative. The vigilante, who may or may not even be related to the deceased person, decides that the justice system agreed upon by the wider community is inadequate, and exacts retribution on their own. They kill the person who accidentally killed the first person. The family of the person who was killed by the vigilante is now incensed. Their own loved one was never given a fair hearing, and punishment was not decided upon according to the rules of the community. Their rage translates into the desire to make the vigilante pay for what he/she has done.
The next thing you know, you have the Montagues and the Capulets picking each other off, with no one knowing who is going to be next because everyone is now fair game.
Where does it end? It doesn't, and everyone is now as guilty as the person they are exacting 'justice' upon.
Even in ancient cultures you see a concern for vigilantism triggering vendettas. In order to prevent this happening, systems of justice were set up whereby the matter of a person's guilt or innocence was looked into by a neutral third party. The evidence had to be gathered, a tribunal had to be set up (even if it is only of the village elders), and the evidence then presented. The tribunal then decided upon the matter, and, if guilt was determined, the punishment was decided upon in accordance with community laws. Because of the social contract, both the accuser and the person being accused, along with their families, had to abide by the decision of the judges, and take no further action against each other.
There will always be those individuals who, like Philocleon in Aristophanes' play 'The Wasps', are addicted to the sense of power that comes from playing the jurist. The damage that they do to both to the accused and the community at large is tremendous. In their thirst for controlling the dispensation of justice, they commit actions that are anything but just. And the end result? Well, President Spence's historic words say it all. Now watch the vignette if you have not done so already.