I think when it comes down to it, humanity is ultimately good. When the common man is faced with what could be considered a moral dilemma, he or she will ultimately take the action which brings the greatest benefit to humanity as long as they don't experience a significant loss. All in all, the good actions committed by men slightly outweigh those with more malevolent aim. This is one big thing that encourages me to continue trying to become a doctor. Every patient that I treat, I know will hopefully recover their health to try to continue to do what is ultimately considered, good.

Of course, good can have several meanings. But that is an argument meant for another to pursue.