Triumph of Evil

I think this philosophy makes sense because the lack of action is presenting no obstacles for evil. If people doing evil don't have anything to overcome, they have an easier task. When presented with some kind of inhibitor, people are less likely to carry out their actions. If no one is stepping in to challenge evil, there isn't anything for the evil to fight. Therefore, it can prevail. Unchallenged in a fight, evil will always arise victorious.
On the other hand, I think that sometimes evil forces prevail even when good people stand up and fight against them. Sometimes evil overpowers good. Sometimes no matter how hard the forces of good fight, they cannot win.
To summarize, I agree mostly with this quote. I don't think that there is only one thing needed to allow evil to succeed. Generally there is more than one factor that allows evil to triumph. It's multifaceted. You can't say that there is only one reason behind something, nothing is truly that simple. Good people that do nothing play a large role in allowing evil occurrences to happen. The situation in Darfur currently is an excellent example of this philosophy. By not declaring it a genocide and kind of turning a blind eye to it, we're allowing it to continue. If someone were to step in and do something, the evil could be reduced significantly. In this instance, the lack of action on the side of good is allowing evil to prevail. But can we say definitively that if good stepped in it could be stopped entirely? I don't think there's an answer that simple. Perhaps multiple aspects have to change in order to stop evil in the world. While the lack of good actions allows evil to spread, it is not the sole reason for evil flourishes.