A thumb pressed against two fingers, and the lean figure of Dr Cruces, head tutor [at the Assassin's School], looming over the startled boys.

"We do not murder," he said. It was a soft voice; the doctor never raised his voice, but he had a way of giving it the pitch and spin that could make it be heard through a hurricane.

"We do not execute. We do not massacre. We never, you may be very certain, we never torture. We have no truck with crimes of passion or hatred or pointless gain. We do not do it for a delight in inhumation, or to feed some secret inner need, or for petty advantage, or for some cause or belief; I tell you, gentlemen, that all these reasons are in the highest degree suspect. Look into the face of a man who will kill you for a belief and your nostrils will snuff up the scent of abomination. Hear a speech declaring a holy war and, I assure you, your ears should catch the clink of evil's scales and the dragging of its monstrous tail over the purity of the language.

"No, we do it for the money.

And, because we above all must know the value of a human life, we do it for a great deal of money.

There can be few cleaner motives, so shorn of all pretense.

Nil mortifi, sine lucre. Remember. No killing without payment."

He paused for a moment.

"And always give a receipt," he added.

-- from "Pyramids" by Terry Pratchett

The above exerpt got me thinking about something last night. The sixth of the Ten Commandments is often misread as "Thou shalt not kill", when in actuality it's translated as "Thou shalt not murder", a significant difference. Killing a criminal in the Hebrew judicial system was not just permissible, it was demanded; so was the waging of war and the killing of enemies on behalf of Yahweh's people. And these attitudes are carried on today, when a legal death sentence or the killing of enemy soldiers on a battlefield is allowed without the punishments reserved for murderers and serial killers.

What is the value of a human life, then? What does it take to make taking a human life legal, or permissible, or conscionable? For the assassins, it's the knowledge that it's just a job; for a military general or a hangman, it's very much the same. They don't kill out of malice or loathing, but they do it on behalf of another party -- the legal system, the national interest, the paying client. They kill for something greater than themselves -- a government, a court, a god. That greater thing has placed a value on the human life before them, and the man then becomes a tool, a living weapon carrying out a sentence given by another.

Adolf Eichmann notwithstanding, it has always been sanctionable to kill another person, as long as you're just following orders or fulfilling the obligations of the law.

There are exceptions in this multicultural world, of course. But I speak as a member of Western civilization, whose mores dominate the world today, whose democratic ideals have been exported to nation after nation across the planet, and with them their central ethics. Killing, we believe, should only be permitted when the greater good demands it. But where does that greater good lie?

Should we follow a religious leader who announces a jihad against another? Or are we expected to second-guess that leader and judge that law against those recorded in the holy books that preceded him?

Should we always be willing to kill if our government asks it of us, as in World War II? Or should we test their rallying cry against our own conscience, as many did during the fighting in Vietnam?

Should we stand by our governors when they stand up for the death penalty? Or should we do everything possible to ensure that possibly-flawed sentences of execution are never carried out?

Should we kill only when it agrees with our conscience?

Or is it enough to just kill for the money?