It is an evil action that becomes necessary for a person to perform as a result of a situation that has no other recourse. A dictionary (www.freedictionary.com) defines necessary evil as: "Something that you do not like but which you know must exist or happen." To go through with a necessary evil, a person admits that they are doing wrong, but their wrong actions are justified by the situation and the circumstance.
In a just war mindset, war is a necessary evil. It is necessary to hold back evil, but at the same time it is still wrong. It should be entered into cautiously, and must always have justification. This is because of the nature of the action. What just war advocates really believe is that war is wrong.
This means that in this mindset, there are some circumstances that evil must be entertained. Another way of saying this is: some circumstances are so egregious it is ok to do wrong. I must boldly question this way of thinking. It is never ok to do wrong. Period. We have to be better thinkers here. By supporting any form of necessary evil, we completely throw any concept of order and justice out the proverbial window.
Batman, is a great example of throwing justice out the window. Batman is nothing more than a vigilante. If you think about it, what the Batman comics teach us is that when evil is so necessary Gotham needs a crime fighter who is not bound by due process and the legal system. He teaches us that our system of police agencies, innocent until proven guilty, and our legal rights sometimes are barriers in fighting evil. This is not a right, but it is what the concept of necessary evil means.
When we promote necessary evil (and just war) we are really undercutting everything that is good.
If we look at 1 Corinthians 10:13 it says:
No test or temptation that comes your way is beyond the course of what others have had to face. All you need to remember is that God will never let you down; he'll never let you be pushed past your limit; he'll always be there to help you come through it. (MSG)What does this say about our situations in life? It seems to be promoting the idea that no matter what the situation, God will provide a way from us. He will provide a way that will prevent us from falling to the temptation of doing evil.