What’s the right thing to do?

The year is 1991. Bush, the elder, is in the white house, and the first Gulf War is underway. Eight British soldiers covertly enter Iraq. They are members of the British special forces, the SAS, under the leadership of Sergeant Andy McNab. Their mission is to destroy a communications link so that Saddam Hussein's forces could no longer launch Scud missiles.

It is late in the afternoon of January 24; the soldiers are hiding in a gully, waiting for the cover of darkness before beginning their work. They hear the tinkling of bells and the piping voice of a child. It's a shepherd boy guiding his flock. The soldiers hold their breath as the boy continues walking directly toward their hideout. If he stumbles on them, the shepherd might alert the Iraqi forces camped nearby.

The soldiers lay low but not low enough. The boy sees them, but he doesn't run. Instead, the shepherd stops and peers at the soldiers curiously. One of the soldiers tries to lure the boy into the gully by offering him some chocolate. We will never know what the soldier planned to do with the boy because the shepherd does not take the bait. He turns and runs like hell. McNab does not know if the boy is going home or hurrying to warn Iraqi forces. But there is one thing McNab knows for sure. If the Iraqi soldiers discover the patrol, he and his men could expect no mercy.

There is one sure way to prevent their discovery. McNab trains the sights of his high-powered M16 rifle on the boy's back, and his finger slowly applies pressure to the trigger. McNab is an expert marksman. He could kill the boy with one shot, and protect his soldiers from potential exposure. But McNab does not pull the trigger. No, he thought, we're the British SAS. We don't kill kids. And he allows the boy to escape.

The shepherd runs to the Iraqi camp and shows their leader how to find the patrol. In the ensuing struggle, the SAS soldiers are outgunned and outmanned. Three are killed, one gets away, and four others, including McNab, are captured and cruelly tortured. Despite what happened, McNab has no regrets about letting the shepherd boy go. No matter the consequences, McNab believed that a British soldier should never shoot an unarmed child-not in peacetime, not in war, not ever.

Now, I'd like to tell you another story. It's about a US special forces soldier named Marcus Luttrell. He is a Navy Seal serving in Afghanistan in 2005. He is leading a small patrol of soldiers on a mission behind enemy lines. Halfway up a mountain, they encounter three Afghan goatherds, one of whom is a boy.

The soldiers keep their rifles trained on the goatherds and debate what to do. If they let the goatherds go, they may return to their homes. Or, they may alert the Taliban to the patrol's presence. Unsure what to do, the soldiers vote on whether or not to shoot the goatherds. They are evenly divided. Luttrell, the commander, holds the casting ballot. He listens to his "Christian soul" and votes to release the captives.

The goatherds go straight to the Taliban and tell them how to find the soldiers. The result is a bloodbath; everyone dies except Luttrell. A second detachment, sent to rescue him, is also massacred.

Unlike McNab, Luttrell sorely regrets his actions. In Lone Survivor, the book he wrote about the mission, Luttrell says that voting to let the Afghans go:

Was the stupidest, most southern-fried, lame-brained decision I ever made in my life. I must have been out of my mind. I had actually cast a vote which I knew could sign our death warrant. . . . No night passes when I don't wake in a cold sweat thinking of those moments on the mountain. I'll never get over it. I cannot get over it. . . . It will haunt me till they rest me in an East Texas grave.

Andy McNab, the British soldier, justified his actions by appealing to a moral imperative-it is always wrong to kill an unarmed boy. The idea that some acts are forbidden, or required, regardless of the consequences is the foundation of what is known as deontological ethics ("Let justice be done, though the heavens may fall.")

In contrast to McNab, Marcus Luttrell judged the morality of his action by its tragic consequences. Letting the goatherds go was wrong, he says. Just look at how many people died. Luttrell's outcome-based view of right and wrong is known as utilitarianism; acts should be judged by their consequences. An action is morally right if it promotes "the greatest amount of good for the greatest number of people."