We made laws to prevent being in a permanent, unproductive state of anarchy. A complex society can't exist if everybody steals and murders each other. Now some of these laws seem so obvious (don't kill, don't rape, don't steal etc) that we couldn't imagine a society without these rules.
We're surpressing all these urges, because of the serious repercussions. We're all feeling lust, pride, jealousy, anger, greed and all the other sins, but we repress them. Well, not all of them. I don't have a religious upbringing and have no problem at all with 'lust' for example, but I have read on the forums here that most of you think it's best to repress these feelings. Why? Fear of repercussions! You believe you have to explain your actions and deeds to a god at the end of your life.
Take away the law (or 'god, who's looking over your shuolder'), and you will see that noble mankind will turn to looting and stealing and killing (You've seen how the Iraqi's reacted when the law was gone, after the Americans invaded! )
This "sense of morality" you speak of is maintained by use of fear of repercussions. It makes us feel safe at night, knowing the police is patroling the neighbourhood, and we have the illusion we might have something that makes us more, better even, than just a primate...
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And then you switch to CNN and you realise you're just another species of animal, trying to make a living.
I think I've changed my mind... Maybe morality is an illusion. Have you heard that news report about Iraqi prisoners being tortured? The experts say that any one of us is capable of murder and torture, given the 'right' circumstances. Your mother, your dentist, the guy that sells used cars down the street and the priest in your church; all potential killers... What a heart warming thought...