I do not like vigilantism. But.

Yes, but everybody's different. Some people never recover from tragedy and spend the rest of their life in such unbearable pain that they become dysfunctional. On the other hand, there are still survivors of Auschwitz living who by all measures returned to normal within a few years, accomplished great things, and were able to put their experience in historical perspective. Some people are just in the wrong place at the wrong time, but they can be comforted by the historical observation that civilization always ends up better in the long run.

It may or may not. As I have noted before, revenge is one of the most primitive human emotions and also, arguably, the most evil of them all. Capital punishment (whether carried out formally by a government or chaotically by an angry mob) of a murderer may actually make the children and other loved ones of the victim feel somewhat better.

What is always overlooked (even here on SciForums, almost no one acknowledges this even though I've brought it up a dozen times) is that another death has occurred, and the new victim of the capital punishment also has children and other loved ones, who are now grieving for him. This is how feuds start, and feuds escalate into wars. "You killed our daddy so we're going to kill your whole nasty family." "You killed our family so we're going to burn down your entire village." "You destroyed our village so we're going to bomb your capital city."

As I have noted, bereaved people must never be allowed to make policy because bereavement almost always causes irrationality. The deliberate creation of a larger number of bereaved people is the most irrational policy ever devised! If you don't believe me, look at the Middle East. They're still killing each other over something that happened so long ago that a good many of the killers couldn't tell you exactly what it was. Today it's just mutual revenge.

Punishment has four purposes, three of which are legitimate, although of questionable effectiveness.

• 1. To take the criminal out of circulation so he does not repeat his crime. This stabilizes civilization by making everyone feel a little safer.
• 2. To rehabilitate the criminal so he does not repeat his crime. This has the same effect only to a lesser degree because rehabilitation is not a science (especially in U.S. prisons) and its success rate is far less than 100%.
• 3. To deter others from committing the same crime by reminding them that they will be punished. The effect of this is very small since a) many criminals are not apprehended or punished and b) people with a "criminal personality" have a very low present-value-discount rate on future rewards and punishment and tend to live for the moment like children.
• 4. To satisfy the primitive desire for revenge. This has zero rehabilitation or deterrent effect. On the contrary, it is more likely to increase the crime rate and destabilize civilization for two reasons: a) by awakening the Stone Age instincts in a previously civilized population and b) as noted, (in the case of capital punishment) by creating a larger number of bereaved citizens (those who loved the person executed) who now want revenge on those who caused their grief.

Very good point. The usual vigilante punishment is execution, often performed in such a barbaric way that civilization is, at least locally, set back a couple of thousand years. See The Lynching Of Jesse Washington for an incident so unspeakable that you should probably not read it on a full stomach, and you may want to skip the photographs. This happened in a large city in the United States (Waco, TX) less than 100 years ago, before a cheering crowd of thousands, including children whose parents thought it would be an instructive experience for them.

And in case you haven't noticed, Texas is still not very civilized.