I find the concept of both
purity and
original sin in children a bit strange.
Children are neither pure nor sinful; they're
amoral little beasts.
Humans are born animals. The main purpose of the 18- (or 20-, or 25-) year period we call childhood is to socialize them into being human beings.
Fortunately, human offspring in general can think and eventually grasp advanced concepts like delayed gratification and enlightened self-interest. If they've been carefully socialized and encouraged to develop those skills, some day they may even display them in practical every-day settings, like lending their favorite blur cd to a friend, holding open the door for the stranger behind them, or volunteering for Big Brothers Big Sisters. But that's just not going to happen in the first 10 years or so.