I've seen this one come around two different ways, the first as attributed to a Maj. L. Caudill USMC (Ret) as below, the second by the guy at Munchkin Wrangler found here.
I think it's a really well reasoned essay, so I'm grabbing it.
With regards to it's author, ... my conscience is satisfied.
Why The Gun In Civilization?
By Maj. L. Caudill USMC (Ret)
Human beings only have two ways to deal with one another: reason and force.
If you want me to do something for you, you have a choice of either convincing me via argument, or force me to do your bidding under threat of force. Every human interaction falls into one of those two categories, without exception.
Reason or force, that's it.
In a truly moral and civilized society, people exclusively interact through persuasion. Force has no place as a valid method of social interaction, and the only thing that removes force from the menu is the personal firearm, as paradoxical as it may sound to some.
When I carry a gun, you cannot deal with me by force. You have to use reason and try to persuade me, because I have a way to negate your threat or employment of force.
The gun is the only personal weapon that puts a 100-pound woman on equal footing with a 220-pound mugger, a 75-year old retiree on equal footing with a 19-year old gang banger, and a single gay guy on equal footing with a carload of drunk guys with baseball bats.
The gun removes the disparity in physical strength, size, or numbers between a potential attacker and a defender.
There are plenty of people who consider the gun as the source of bad force equations. These are the people who think that we'd be more civilized if all guns were removed from society, because a firearm makes it easier for a [armed] mugger to do his job. That, of course, is only true if the mugger's potential victims are mostly disarmed either by choice or by legislative fiat--it has no validity when most of a mugger's potential marks are armed.
People who argue for the banning of arms ask for automatic rule by the young, the strong, and the many, and that's the exact opposite of a civilized society. A mugger, even an armed one, can only make a successful living in a society where the state has granted him a force monopoly.
Then there's the argument that the gun makes confrontations lethal that otherwise would only result in injury. This argument is fallacious in several ways. Without guns involved, confrontations are won by the physically superior party inflicting overwhelming injury on the loser. People who think that fists, bats, sticks, or stones don't constitute lethal force watch too much TV, where people take beatings and come out of it with a bloody lip at worst. The fact that the gun makes lethal force easier works solely in favor of the weaker defender, not the stronger attacker. If both are armed, the field is level.
The gun is the only weapon that's as lethal in the hands of an octogenarian as it is in the hands of a weight lifter. It simply wouldn't work as well as a force equalizer if it wasn't both lethal and easily employable.
When I carry a gun, I don't do so because I am looking for a fight, but because I'm looking to be left alone. The gun at my side means that I cannot be forced, only persuaded. I don't carry it because I'm afraid, but because it enables me to be unafraid. It doesn't limit the actions of those who would interact with me through reason, only the actions of those who would do so by force.
It removes force from the equation...and that's why carrying a gun is a civilized act.