The following is from the first season, episode five. It's the first real speech where we see Jack emerge as the leader of these "survivors". His speech, is straight, to the point and well can be taken as advice for most of life. "If we do not find a way to live together, we will die alone".
This theme comes back over and over again throughout the six seasons of this show. And for some reason I know it will again come into play during the finale. Its just too important.