I wonder if one could sum up this humanitarian principle in a pithy aphorism that immediately tells you on what side of the question someone's ethics can be found.
And then I wonder if one, whether subscribing to the pithy aphorism or just the ethical principle it expresses, might return to the topic of methods of execution of least harm.
I think the question of least harm can be addressed without regard to whether or not one opposes execution itself. I have various reasons for being against execution, but I don't think that makes it impossible to speculate on how it might best be done when it is. It's all theoretical anyway.
But I don't think it can be addressed without regard to the more complicated question of what various people consider to be, or not to be, the difference between punishment and elimination. An execution is inherently fatal, and almost inevitably stressful, but the method of doing it is seriously dependent on requirements that are difficult to reconcile, the requirement of punishment and conscious awareness of it while it happens, and the desire to make it humane and not too gruesome.
I think there are also some issues which nobody can answer unless we find a way for dead people to report back, among them the question of whether a short and very intense pain is better or worse than a less intense pain over a longer period.
It would, after all, be pretty quick and effective to use a sharp guillotine. Arguments about former times in which the blade got dull are hardly relevant, since even in bloody Texas they would have time to sharpen it and clean it up between uses. We slaughter cows with a pneumatic bolt that is quick and certain, and plenty of tyrants and soldiers have discovered that a good sized pistol to the back of the head is pretty effective as well. I'm guessing, though I hope I never find out, that this is intensely painful for a very short while, but it's obviously over pretty quickly. And we euthanize pets in a manner that appears to be painless, though of course they have the advantage of not understanding what is to come.
I think if you decide execution is appropriate, and if you then decide that the point of execution is simply to remove an incorrigible person from the earth, it can be done with reasonable alacrity and a minimum of fuss and prolonged agony. But there is no way it will not be fatal, no way it will not be a dreadful prospect for the person being executed, and what constitutes "instantaneous" is debatable. Demanding that it be done with some imagined veneer of dignity, consciousness, or last minute repentance complicates it, as do issues of whether there is an afterlife. Or, to borrow once again the wise words of Tuco the ugly, "If you need to shoot, shoot, don't talk."
