I still don't know why in English it's called "common" sense, apparently some guy was optimist while calling it that. In my tongue (Italian) it's known as "good" sense.
Anyway, it's the ability to understand things that "are obvious" only to people WITH common sense. This sense is not that "common", look at how many people vote liberal, are communists despite what happened to Russia, and so on. The list is long folks...
Not to be confounded with "intelligence" aka I.Q. A scientists probably doesn't know what the FUCK is going on next door to him and if he sees a green light across a street full of cars he starts crossing.
Common sense alone, when spoken out loud makes people who lack common sense idiots, because for a moment they realize how stupid they really are. "You probably shouldn't have bought that many weed to sell in the street, now the cops busted you". "If you didn't get in the car so drunk you wouldn't have had the crash". And so on.
When people lack common sense they start a process of saying bullshit one after another and will go on forever because they lack insight (this "common sense"). This is known as "philosophy", or as getting out of college to become a musician of some sort and being proud of "not caring about money". When having common sense, little or no thinking ahead are required. You just do what you have to do, what you see is right. If something falls, you pick it up. If there's a problem, you solve it. If something doesn't work, you don't use it ever again.
The whole umanity could be divided between people who have "common sense" and people who don't. They develop in opposites directions, do things the other half thinks it's "stupid".
In my experience common sense is NOT a present from experience or even external influence. Sure it gets better with time, but I've seen too many morons with a decade of moron experience and they still don't get it. Either you're born with it or you're not. Good nice people have communist children. How sad. Go figure...
And common sense does NOT have colours or a fixed ideology. You normally would thing it's a right-conservative thing but I wouldn't have voted retarded bush for the second time. It simply is the right thing to do. Period.
Heavily suggested book: the Art of War by Sun Tzu.
A guy who for many years keeps throwing away his whole salary in less than a week to do lines then has to get dumped by a stupid bitch he calls "girlfriend" to realize what was going on.
Being 23 and still criticizing "capitalism as it exploits the poor".
Any stupid dumbass woman who thinks I ever loved her when she couldn't realize I fucking HATE ignorant people.
People who do heroin.
And so much many more people lacking common sense...