It seems to me that much can be understood from the consideration of opposites.  Pitting one thesis against its antithesis brings clarity and facilitates discussion.  While such categorical thinking can disguise subtlety as simplicity, it can also help to make plain the underlying principles of a matter.

Consider, is mankind good or evil?  At one pole is the goodness of mankind and at the opposite pole is the depravity of mankind.   The one is defined as the negation of the other.  Either/or. 

The problem with dichotomies is that there is always the argument in the middle.  In this instance, mankind is both good and evil.  Man’s goodness tends to be overrated and the imperfection, while self-evident and generally acknowledged, is generally dismissed.  Most would grant that mankind can be both noble and base, devious and self-serving, at the same time.  A mere glance at our popular culture shows how we would posit all the bad stuff over there and all the good stuff over here.   So long as the evil is not in us we can dismiss it or even fight it. 

Unfortunately, good and evil is not a matter of us versus them; it is more a matter of us and them.  The bad stuff is in us too.  The problem here is what the Bible calls sin. Man has a sinful nature.  Whether we deny evil in ourselves or justify evil in others we behave without justice.  How shall we judge when we are guilty ourselves?  Whom shall we appoint as judge who is not also guilty?  There is only One who is worthy.