Environmental Impact

Recently, I was at a friend's house, when another friend was dropped off by her prius-driving parents. We both commented on how responsible and environmentally conscious her parents were. While I praised her parents and suggested more people should try to cut back on pollution and be more aware of their carbon footprints, this friend of mine felt she could be wasteful because of this other family. She said that it averaged out and was therefore justifiable for her to be wanton with gas and paper products. I find this mentality to be deeply disturbing. The idea that one's willingness to negate another's attempt to do something positive is simply revolting. The idea applies not only to environmental principles, but to every other issue that faces us both as individuals and as a society.
If we each do our part and assume no one else will do theirs, we will be that many steps closer to improving the human condition. At the same time, refusing responsibility because someone else is "doing my share" will take us back several steps. I feel this principle (while it lends itself to a more negative outlook) will help us all improve the world we are all stuck sharing.