Can you think of a situation in which properly using the three criteria above would leave the need for punishment (the state taking vengeance) unfulfilled?

Okay, that’s fair enough. But I don’t think we can leave punishment ENTIRELY out of the equation. Less important than protecting the public, but I think it still needs to be a recognized goal.

I don’t dispute that. However, deciding what “proper” punishment is for an infraction (or whether a punishment is even proper — insert the lyrics for “Only a Lad” here) is increasing hard in a pluralistic society; there isn’t a schedule of weregild that we can all agree upon.

I think as well that there ISN’T an instance (certainly not one I can conceive of) in which “someone is highly unlikely to commit another crime, and punishing them wouldn’t stop any third parties from committing similar crimes.” Those people who would commit a one-off crime for a specific circumstance that’s not likely to ever come up again (I’m now having flashbacks to ALL of the Columbo TV-movies) are the most likely to be deterred by the awareness of a severe penalty if they’re caught.

Let me be clear: I have as strong a visceral urge to feed vile monsters into a slow woodchipper feet-first as much as the next guy, and as I indicated, I have no problem with the death penalty as such. But if we concentrate on punishment as the PRIME motivation for criminal penalties, we’ll always get caught up in questions of ultimate culpability vs. societal influence, mental health, etc. Whereas if we were to privilege the principles above in making decisions about criminal penalties, then the issue of punishment would largely take care of itself, either by being fulfilled in a penalty prescribed by adherence to those principles, or by having the action requiring the punishment curtailed in the first place.

For instance: Decarlos Dejuan Brown Jr., the piece of human excrement who killed Iryna Zarutska at random, was walking free because he was released with a pinky promise by a judge who had relied entirely on whether “punishment” was warranted for previous infractions and whether someone with his mental problems was truly culpable. Whereas if she had used the criteria above in rendering her judgment, it’s very likely that Brown simply would not have been at liberty to to what he did. And if his current committed to a federal medical facility (due to being adjudged as incompetent to stand trial) were committed first and foremost not to the stated goal “restoring his competency” but of protecting of the innocent at large, then the odds of him every being able to commit further atrocities would be greatly reduced.

Of course, the problem of getting from where we are the the adoption of the principles above is gargantuan enough to render the thought experiment almost entirely hypothetical with the application of a flux capacitor. But even in cases where there’s no reasonable means to effect a societal change, we should still devote thought to formulating what a more perfect society would look like, so that we can recognize incremental changes in that direction.

It’s not necessarily a noble goal or a logical goal, but there’s something in us that demands, “When one among you harms another, he must be punished.” A big part of what makes society works and keeps it from devolving into feuds and vendettas is the bargain that, if someone is wronged, the state will take vengeance on that individual’s behalf.

Even if it’s someone is highly unlikely to commit another crime, and punishing them wouldn’t stop any third parties from committing similar crimes, I doubt anyone personally involved would be satisfied with, “Oh, well. You get your one free murder. As long as you don’t do it again, you can go through life happily.” That would likely lead to a lot of crimes having a de-facto death penalty, as the victim or someone close to him decides that it’s time to make use of HIS free murder…