There are two ways of looking at this:
One is a concept and sees the interdependence of all opposites. It says we should not hold a position of good against evil. One or the other cannot eventually stamp out the other or “win” because if you don’t have one what is the other? If there is no evil, what defines “good”?
The second is a reality. All actions contain some aspect of each. The Yin/Yang symbol is a great representation of this. “Any attempt to go toward either extreme of the continual balance between yin and yang will be ineffective, self-defeating, and short-lived.” (Rasmussen). “The [wise] person knows any evil will soon be replaced with good, the fool is forever fruitlessly trying to eliminate evil.” (Rasmussen).
