I'm watching the episode "Enemies" right now and the differences in Buffy and Faith's upbringing made me think of the nature and nurture dynamic in how children turn out as adults. In this episode Buffy and the gang find out definitively that Faith has turned on them and is on the mayor's side. Before Faith is about the torture Buffy she explains why she has turned to the dark side and why she hates Buffy.
We had always known Faith was the bad girl who didn't have any family or friends. But for a while she fought on the good side. In this episode Faith reveals that her mother was an alcoholic. And unless I missed it, she doesn't even mention a father. So needless to say she comes from a pretty bad home. Thus when it comes to the nurture part of Faith's upbringing she didn't make out well.
Compare that to Buffy, who despite her parent's divorce while she was in high school, had a pretty standard upbringing. THe biggest difference seems to be Buffy's dad. Even though we see very, very little of him in the series, I think we can assume he was an average dad during her childhood. Faith didn't even have the barely existent father that Buffy had since the divorce. This is probably why Faith was attracted to the affection the mayor showed her. When she thinks Buffy and the gang abandon her, Faith probably internalizes their actions as the same thing her parents did to her, thus the hatred towards them and the desire to please the mayor who has adopted her. Like Spike says of Buffy when he is explaining why she has survived for so long, Buffy has family and friends. Those are important aspects of nurture that help all of us become a decently functioning adult within our society.
The nature aspect of the two characters is pretty similar. Both are very pretty, healthy, and smart women. By most accounts they did well in the nature side of things. And to add onto that, they both get chosen as slayers and possess awesome powers. In real like looks, health, and intelligence vary to some degree between people and at least in part shape how a person turns out as an adult. Sometimes I find it difficult to sort out what had more influence on certain aspects of a person's persona, nature or nurture. What Buffy and Faith allow us to do is to essentially hold nature constant and see how important nurture can be to a person.
What I also like about this episode is Angel's role in it. Angel has something things in common with Faith, mainly that he knows what it is like to kill someone and be on the bad team. Because of his shared experience, Angel is sympathetic to Faith and seeks to help her. While Angel probably has less of a reason to have turned bad based on what we know about his family life, he understands that people aren't just born evil, that things happen in their life that are beyond their control that can have a negative impact on them. Even thought Angel's redemption was forced upon him, he also understands that people can change for the better as we see in his own series Angel is instrumental in helping Faith turn her life around.
That dynamic of Angel helping Faith find redemption is probably my favorite thing about the show. My favorite characters are the ones that have major flaws (Spike, Cordi, Wesley, Angel) but who work through them to become better. Not that it was easy for those characters to change and become better, but I wish the process was as linear for people in real life as it is in the show.