This is the third post in a series on Good and Evil.
Jesus Christ is the Prince of Peace.  
Following his teaching and example, Christians seek to settle conflict in non-violent ways as a matter of principle.  Non-violence is our first choice and we pursue it well beyond the point at which others might wonder at our sanity.
Conflict often occurs between two good and reasonable parties whose points of view differ.  Violence is never in order here.  In fact, well-managed, respectful conflict of this sort can arrive at new insights and deepened relationships.
But sometimes conflict results from evil.
In the previous post in this series I tried to make the point that evil is the anti-peace.  Evil is utter resistance to God’s order of things.  God designed the universe to hang together like a Luminous Web, to borrow a Barbara Brown Taylor title.  
There is only God’s order.  Any divergence from that order or alteration of that order becomes destructive and debases the life God intends for us.
Promising a more just or more lucrative or more pleasurable or more vaguely free order, evil merely tears apart the threads that hold together what God intends to be a peaceable kingdom.
Christians are called to resist evil.  And as a last resort, we may use violent means to stop the destructive forces of evil.

Before I go one step further, I will acknowledge that there are some who will find this piece completely unpersuasive.  Our starting points are so out of synch that they can never reach my conclusions.  
If for you there is no such thing as evil—evil, you might say, is only what we call those things that threaten us in some way—then what I’m about to say will seem utterly misguided.
Or perhaps you are what might be called a Pacifist Relativist.  In your view, there is no universal, absolute moral law.  So, there can be no such thing as evil.  However, you make an exception to your relativism.  Any harm done to others is wrong.  
Without an absolute moral law I cannot see how one can pursue peace with moral zeal.  But my point here is that you too will find what I’m about to suggest unsophisticated and maybe even a little dim-witted.
However, if you routinely pray The Lord’s Prayer and mean it, then you should at least be open to my suggestion.  Remember, we pray, “Lead us not into temptation, and deliver us from evil.”  Jesus himself taught us to pray for deliverance from evil.
Some will immediately respond with these words from Jesus: “All who take the sword will perish by the sword.”  (Matt. 26:52b)  
And it is true that all who strike out in anger, those who seek nothing more than to settle a personal score, and those who inflict pain for the perverse joy of it will themselves be consumed by their own destructive ways.
Nevertheless, violence can justly be used to protect the weak from evil.  As the Psalmist says, “Rescue the weak and the needy;
deliver them from the hand of the wicked.”  (Ps. 82:4)
And contrary to the faux wisdom of a certain crude bumper sticker (Waging war for peace is like f*%#g for virginity), it is not a contradiction to employ violence to achieve peaceful ends.  My point rests in part on an apparently contradictory remark that Jesus made.
Jesus said, “Do not think that I have come to bring peace to the earth; I have not come to bring peace, but a sword.”  (Matt. 10:34)  
As St. Thomas Aquinas points, there is a kind of illusory peace.  Open hostilities have ceased, but there is the constant threat of terror.  People cope in misery or live with lies or scurry to stay under the radar screen of oppressive, coercive powers.
This is not the peace that Jesus came to bring.  In fact, in a later post, we will see that he comes to bring the final sword to a debased existence that equates peace with a level of misery and perpetual violence that we can tolerate.
It may seem Christian to wait passively upon the Lord to eradicate evil.  
But just as surely as he teaches us that we are his instruments in addressing poverty (Matt. 25:31-46) until he comes again, so too he instructs us to struggle in his name against evil.  As St. Paul says, properly authorized violent means can serve God’s just purposes.  (Romans 13:3-4)
Much has been written about Just War Theory since Thomas Aquinas’ day.  But the basic principles remain the same.  
Proper authorities must sanction violent means for the greater good.  Violence is never appropriate in the service of personal, self-interested feelings.
The cause must be just.  In other words, we can justify violence only as a response to aggression against us or in defense of those who cannot defend themselves.
And finally, the motives must be just.  As contradictory as it may seem to some, violence can be used to restore peace by resisting the evil bent on destroying peace.
All of this is well and good for rational, objective minds.  In other words, somebody unlike all the rest of us.  It is difficult for us to sort out our motives.  We can disagree about what is evil.  We can disagree about when violence is needed.  We have all let our anger get the better of us.
How do we fallible creatures make the decision to use violent means in the service of justice and peace? That’s our topic in the next post.