My last post, "How Can We Condemn Boston Murders and Excuse U.S. Bombing of Civilians?", has provoked lots of commentary, including a vigorous discussion on reddit. The larger question people are wrestling with is when, if ever, lethal force is justified. Here is my attempt at an answer, which I originally presented in The End of War and in a column last year:

History abounds in challenges to peace-lovers, which I call damned-if-you-do-or-don’t dilemmas. Should American colonialists have violently resisted British rule? Should Lincoln have waged war to preserve the Union and end slavery? Should the U.S. and other nations have intervened when Saddam Hussein seized Kuwait in 1990? When Serbians carried out ethnic cleansing against Muslims in Kosovo? When Hutus started slaughtering Tutsis in Rwanda? When China squashed Tibet’s attempts to gain independence? Let’s say that Nazi Germany had not invaded any other countries but had carried out its plan to exterminate all German Jews. Should other nations have attempted to stop the slaughter? When, if ever, is nonviolence less moral than violence?

These are the quandaries that just-war theory purports to answer. Just-war theory has a checkered history. One of its founders, the fourth century cleric Saint Augustine, was keen on holy wars waged by Christians against infidels. He argued that killing sinners and non-believers is righteous, because it stops them from sinning. This logic helped inspire the Crusades and European conquests in the Americas. Just-war theorists have also reasoned that war, because it is so awful, should be waged ruthlessly to end it as quickly as possible. This logic justified Sherman’s brutal devastation of the South during the Civil War; Churchill’s decision to bomb civilian populations in Germany; Truman’s choice to drop atomic bombs on Japan.

Virtually all modern warriors claim–and even believe–that their cause is just. Some wars, especially “humanitarian interventions” undertaken to help others, are clearly more just than others. But once wars begin, even warriors fighting for just causes often behave unjustly. The armed intervention of the U.S. and its NATO allies against Qaddafi two years ago demonstrates this truth. Bombs dropped by NATO planes killed not only Qaddafi’s troops but also civilians NATO was supposed to be protecting. The Libyan rebels, after gaining the upper hand in certain towns, reportedly killed civilians loyal toward Qaddafi, prompting reprisals from Qaddafi loyalists. This same terrible pattern has unfolded in Syria.

Quakers, Jains and other pacifists consider the concept of “just war” to be an oxymoron. Needless to say, I’m sympathetic toward this viewpoint. I believe that NATO’s intervention in Libya—like the U.S. invasions of Afghanistan and Iraq—was a mistake. But I certainly relate to the Obama administration’s empathy for and desire to help helpless civilians being attacked by a cruel bully. Could I have stood by if I had the power to stop, or try to stop, Qaddafi? What about Syria’s Assad regime?

I believe people have the right to defend themselves against violent attacks. We also have the right, and sometimes the duty, to help others being threatened by bullies. But given war’s terrible unpredictability, and its tendency to exacerbate rather than solving problems, we should do all we can to solve damned-if-you-do-or-don’t dilemmas nonviolently—or, if that fails, with minimal force. I don’t have any special formula for determining exactly when and how to use force. I just have a few simple—simplistic, some might say—rules.

First, we should heed the Hippocratic command to do no harm. In other words, whatever we do, we shouldn’t make a bad situation worse, which is just what the U.S. and its allies did in Afghanistan, Iraq and, arguably, Libya. We should stop using mines, bombs and other weapons that kill indiscriminately. That includes the drones that the Obama administration has deployed to carry out assassinations in Iraq, Afghanistan, Pakistan, Yemen and probably elsewhere.

Minimizing casualties, even of combatants, should be the highest priority. The manner in which police employ force should be the model. In the U.S. and most other democratic countries, police are legally required to avoid hurting civilians and even criminals. If police know that a psychotic, armed killer is holding hostages in a building, they don’t immediately bomb the building or storm it with machine guns blazing. In fact, they try to capture rather than kill the killer so that he can be tried by the justice system, as occurred last week in the case of the suspected Boston bomber. Often, this means that police patiently try to talk the criminal into surrendering without hurting his hostages.

The approach I’m advocating resembles the “just policing” philosophy of the theologian Gerald Schlabach. He sees three key differences between police work and conventional warfare. I’ve already mentioned two: Police officers place the safety of civilians above all other goals, and they strive not to kill criminals but to bring them to justice. The third difference identified by Schlabach is rhetorical. Whereas wartime leaders often employ charged, emotional language to rally a nation against the enemy, competent police officials seek to tamp down rather than inflaming emotions.

These rules are restrictive enough, but I have one more that, if followed, may result in even fewer armed interventions: Whatever our response is to a damned-if-you-do-or-don’t dilemma, we should formulate it with the larger goal of abolishing war, and even the threat of war, once and for all. This means that, if we employ violence, we must do so in a way that does not legitimize violence as a solution to problems. This may seem to be a tricky, even impossible, proposition, but police pull it off when they’re doing their jobs well.

The end-of-war rule demands that we consider not only the immediate consequences of our actions but also how they will be perceived by others. Will our actions be viewed as disproportionately violent? Will they provoke reprisals? Will our intervention, which we claim is purely altruistic, look to others like muscle-flexing? A demonstration of our nifty new stealth fighter or drone? A reminder to other nations around the world of our overwhelming military superiority? An attempt to seize oil reserves? Are our actions consistent with the principle that war is immoral and needs to be abolished? Or will they make it easier for other groups to justify their violence?

These questions are directed primarily at the U.S., which—let’s face it—is a major impediment to world peace. I love my country, but I am often embarrassed by the chasm between our lofty rhetoric and our actions. We denounce Al Qaeda, rightly, for the moral nihilism and illegitimacy that it demonstrates when it kills thousands of innocent American civilians. So how does the U.S. respond? By invading two countries and killing thousands of civilians who had nothing to do with the 9/11 attacks.

We claim to revere peace and human rights yet we embark on wars of choice, in which we treat alleged enemies and even innocent civilians cruelly. We pay lip service to the principles of national sovereignty and international law while secretly carrying out deadly drone and commando raids. We spend as much on arms and armies as all other nations combined, and we are by far the biggest arms dealers on the planet. We are guilty of shameful hypocrisy. If we practiced what we preached—if we showed through our actions that we recognize how wrong war is—we Americans could lead the entire world to an enduring peace.