Kevin Drum, unsurprisingly, has the most thoughtful response to Eugene Volokh's support for painful punishment.
Aside from material advances, the primary achievement of human civilization — slow and spotty as it's been — has been moral progress: we don't keep slaves anymore, we don't execute heretics, and we don't allow eight-year-olds to work 12-hour days in front of power looms.This is powerful and largely correct. The one thing missing is the recognition that moral progress is not equally distributed, either around the world or in our own countries or towns. To trade the sword for the pen is civilization; to refuse to take it up again when faced with the need of others is decadence. If the promise of great cruelty deters sadistic monsters (like the one who inspired Mr. Volokh's original post), then we as a civilization have no right to eschew it.
But this progress has been tenuous and halting, with our inner demons never far from the surface — and accepting a reversal in our slow march toward moral improvement is playing with fire: as both recent history and current history demonstrate, the veneer of civilization continues to be mighty thin.
Mr. Volokh's position has been characterized as "meeting savagery with savagery", with the implication that we, the executors, are demeaned by the use of crual punishments. This may even be true, but it is beside the point because this is not about us -- it is about the victims and possible future victims. Turning the other cheek may or may not be right; turning someone else's other cheek is never so.
I believe that it is our moral duty to meet savagery with whatever tools will be most effective, up to and including the equally savage. We should not seek cruelty, but we should not reject it to spare our own sensibilities. The occurrence of any heinous crime is a failure of civilization, greater than the failure inherent in cruel punishment. Vindictive disapproval (to borrow Mr. Kleiman's terminology) can serve the victim's interest and limit the damage to society. This is the first-order effect of punishment, while Mr. Drum is considering the second-order effect. The real meaning of Mr. Drum's argument is that we must never err on the side of cruelty if there is doubt as to its efficacy.
My omission here is in assuming a monolithic "we". In practice, each society reaches an effective consensus, which changes through time, as to what retributive punishments can be considered.
In the United States today, we have reached an unclean compromise. Setting aside the (rare) death penalty, the most cruel punishment is confinement in cells which are mandated to fairly high nominal standards of cleanliness and roominess -- so the State has the appearance of highly civilized mercy. Then, in practice, standards slip and the State turns a blind eye to prisoner abuse at the hands of other prisoners, so as a practical matter imprisonment is a mixture of bland inconvenience and brutal abuse.
Those who wish for harsher punishments ignore this problem because it has an effect they find desirable; those who wish for greater leniency might wish to change the situation, but their proposals tend to a nominal level of leniency which is completely unacceptable to society. We could reduce jailhouse brutality and prisoner rape, increase the deterrent effect of prison terms, reduce their value as a training ground for criminals, and simultaneously save money -- simply by isolating prisoners more in smaller cells, instead of giving them just enough "rights" to let them create jungle societies.
[Update: expanded and slightly rewritten after reading M.A.R. Kleinman's detailed post.]