I think we linked this piece once, but I can't remember. It's from Munchkin Wrangler (h/t, Right Wing Prof), and begins thus:
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 gangbanger, 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.
Read the whole thing. Here's a nice piece on handgun selection for self-defence.