the dialectic of good and evil

We were talking about dialectics today in Anthropology class, and Seibold explained them as being dichotomous concepts along a continuum. (In this case, it was the Positivist and Interpretivist approaches to anthropology). In trying to give examples to the class, Kathy listed good and evil as being a dialectic; most of us aren't purely, purely good, and most aren't pure evil. We usually fall somewhere in between. My mind immediately raced for examples of where I would fall on the dialectic, a self-reflective description: "She is, outwardly a good person. She'll do things for the people she loves; friends, family, someone desperately in need. But she's not really selfless. She's got the usual self-preserving tendencies. She's not necessarily more selfish than most, just more honest with herself about her selfishness. Unabashedly selfish, let's say. Most of the evil in her blood is released through silent brooding, feelings of resentment, and covert social sabotage to achieve her own ends. And most of her evil is caused by feelings of jealousy, inferiority, and insecurity. But she is very subtle with her evil, and makes sure to cover her tracks. I mean, who doesn't want to be viewed as a good person?"