I was just re-reading a couple of articles...

Barack Obama said during his presidential campaign that Reinhold Niebuhr was one of his favorite philosophers.

I've been reading "Mere Christianity"

Niebuhr said, "we use evil to prevent a greater evil"

and

“There are historic situations in which refusal to defend the inheritance of a civilization, however imperfect, against tyranny and aggression may result in consequences even worse than war”

Lewis said, "There is no evil without good"

What is evil?

some would say that "evil" is the opposite of "good"

Lewis says that evil is not the opposite of good, but rather it's the perversion of good.

There can be no evil without good.

Unless we have the ideal to compare an action to, there is no concept of what it means to violate God's Law.

is having food to eat "evil"?  No, it's a good thing, but to have it because you stole it is a perversion of the good thing (having)

Unless you have a concept of what "truth" is, the term "lie" has no meaning.

Rest is a good thing...perverting rest into slothfulness is not.

Wine is a blessing, drunkeness perverts that blessing into something that is not good.

Back to Niebuhr...

there is a concept of "just war".  Some buy into it, others don't.

When Niebuhr said, "we use evil to prevent a greater evil", he was referring to war.  If war is always "evil", then protecting a nation against attackers is using evil to prevent greater evil.

Questions:

If evil is not the opposite of good, but rather the perversion of good, what is the good that war is the perversion of?

If war is used to protect and prevent evil, is it "just war" evil?