Two of my friends are arguing about witch-burning, and thanks to the Internet I get to eavesdrop.
In this corner, longtime friend Eugene Volokh, making arguments of expediency and self-interest rightly understood:
the conventional understanding of witches was that they got their powers through an alliance with satanic forces, and that they acquired those powers partly to use them against innocent people (or else why did they need the powers?). Punishing them is thus no different from punishing someone who got some very nasty weapons by dealing with the Mafia, or someone who has — but has not yet used, and as to whom there is no firm evidence that he is about to use — a radiological bomb that he got from a terrorist organization with which we are at war.
Witches: Reader Paul Forsyth points out that C.S. Lewis beat me to my witches observation by decades (not surprising — my point was pretty obvious). Forsyth quotes Mere Christianity, p. 26:
But surely the reason we do not execute witches is that we do not believe there are such things. If we did — if we really thought that there were people going around who had sold themselves to the devil and received supernatural powers from him in return and were using these powers to kill their neighbors or drive them mad or bring bad weather, surely we would all agree that if anyone deserved the death penalty, then these filthy quislings did.
In this corner, longest time friend Brad DeLong, who has taken on a more mystico-religious cast than he exhibited as a kid, but one tempered by an understanding not just of sin but bounded rationality,
On the contrary, there is a HUGE difference between burning somebody alive because you think she is a witch, and killing the possessor of a radiological bomb acquired from a terrorist organization. THERE ARE NO WITCHES. WHEN YOU BURN A “WITCH,” YOU ARE TORTURING AN INNOCENT, INTELLIGENT BEING TO DEATH SIMPLY BECAUSE YOU HAVE A FALSE CONCEPTION OF THE WORLD.
There are times—like after reading the Rubin-Weisberg book, In an Uncertain World—when I think that the hallmark of true intelligence is to recognize that one may not know everything, and that one should take special care to avoid actions that are impossible or very costly to reverse—like burning a “witch”, or attacking Iraq in the belief that even though you don't know of any links between Saddam Hussein and Al Qaeda you're bound to find a piece of paper that will serve as such somewhere in Baghdad. Even if I believed in witches, I wouldn't burn them. Deprive them of the chalk they use to draw pentagrams, yes; separate them from their familiars, yes (sorry kitty); deprive them of the ability to use their knowledge of the magical laws of similarity and contagion, yes; but kill? No.
As Oliver Cromwell said: “I beseech you, in the bowels of Christ, consider that you might be mistaken.”
Often when friends argue, I'm reminded of the southern politician who, when asked about a very controversial issue replied, “Some of my friends are for it, some of my friends are against it, and like any gentleman, I stand with my friends.”
But on this one I think my friends are talking past each other. Eugene offers a lawyer's hypothetical: “suppose we were convinced that the facts were other than we know them to be, what would be the right response?” That's how lawyers talk. That's how we think. That's even how we play with ideas.
Brad's reply in some sense does Eugene the honor of taking the hypothetical too seriously. Brad's reply is of the form, “suppose we were convinced of a set of facts that we should know better than to be convinced of? Well, that shows we're nuts. Don't do radical things like kill people when you are nuts.”
And, in this case, both my friends are right. I think that Eugene expressed his view more elegantly. And indeed, were we faced with incontrovertible proof that evil Satan-powered witches were stalking the earth, it would fit in with our general jurisprudence to punish them for conspiracy even if we were unable to serve the ringleader of the conspiracy.
Brad's reply isn't as elegant as Eugene's, because there's a sort of logical leap from the jurisprudence of 'witches' to economics and politics. And too many caps. But nonetheless, I think Brad is more right: not only is it wrong to kill both “witches” and witches1 but because current events — running from Guantanamo to the Padilla case perhaps even to Abu Ghraib, not to mention the Innocence Project — do offer very cautionary tales about the dangers of believing your eyes when you start seeing 'witches' in real life.
 At this point, every legally trained reader, not to mention readers of fantasy novels, is going to say, “but the whole problem with Satan-powered witches is that you can't lock them up — they escape — so that a prison sentence isn't a meaningful punishment.” To which I, also legally trained, reply that therefore we can't even have a trial, because that requires detention, so our 'kill the witches' policy is now a 'shoot on sight' policy, which since they are too dangerous to get close to, means it is now a 'shoot on suspicion' policy, which means it is time to adjourn this argument and go read up on slippery slopes.