A hypothetical just society would use the death Penalty as a form of punishment.

First, while I will concede that social stability is important for protecting people's rights, it is crucial that we not neglect other aspects of what makes a society just. A tyranny is not necessarily socially unstable; it is entirely possible for an unjust society to be relatively stable. You note that "The first priority of a just society, therefore, is to ensure it can remain just and look to other values." Let's examine, then, what sorts of values we promote with the death penalty. The clearest message sent by the death penalty is: "killing is not inherently wrong". If it is perfectly OK to execute people even when they pose no immediate threat (i.e., it's not self-defense), then the message we send is that murder can be justified, as long as the person in question _really_ deserves it. Whereas banning the death penalty makes it exceedingly clear that killing people is never the answer to a problem, allowing it, even if only in special circumstances, leaves the rightness of killing a certain person up to the discretion of individuals. We promote a culture of death and of retribution, rather than one of cooperation, tolerance, and working to resolve problems nonviolently. More generally, the death penalty dehumanizes people, making their right to life conditional upon their actions rather than inherent. It promotes the socially harmful attitude that not all people deserve to live, encouraging more brutality and less compassion from the citizenry. We must also keep in mind that innocent people are often killed by the death penalty--including people whose names would have eventually been cleared had they been given a life sentence. Surely we do not want to say that a just society needlessly kills innocent people. See http://forejustice.org... Even if the death penalty were necessary to maintain social stability, then, it seems that to the degree that it promotes social stability at all, it promotes it at the expense of its justness, its morality. And since the subject of debate is what a just society would do, not merely what a stable one would do, this is a crippling problem for the "Pro" side. You say that society is constantly at risk from criminals it doesn't execute, but you could use that logic to justify executing all people who ever break the law; where do you draw the line? That aside, the risk is not really that great from imprisoned criminals. Moreover, even disregarding the fact that treating people humanely benefits society in itself by promoting good values like compassion, forgiveness, and nonviolence, there are many other potential benefits to society from not executing criminals: it saves money and resources (the average U.S. execution costs $2-5,000,000) which can then be put into important social causes; prisoners (even disregarding ones that can be fully rehabilitated) can be put to work in various ways to benefit society and make up for the damages they've caused, and then some; and it spares the lives of inmates who were falsely convicted and could later be cleared and return to being productive members of society. For more details, see http://www.econ.ilstu.edu... Nor is the death penalty the only recourse available for preventing crimes from people who are already imprisoned; there are plenty of other options available, such as solitary confinement. Some prisoners might even consider the death penalty a blessing by comparison. Presumably you acknowledge that the death penalty does not serve as a significant deterrent in the vast majority of crimes, and studies bear this out. Criminals, especially ones acting out of passion or desperation, rarely think ahead far enough to consider what possible punishment they will receive if they are caught. While it might seem on paper that a criminal would be more deterred by the death penalty than by a life sentence, in practice that eventuality is usually too abstract to significantly influence the behavior of someone, especially if they don't expect to be caught by law enforcement anyway. You thus focus only on a very specific and unusual instance: rebels seeking to overthrow the government. Here, I am not sure that your quoted arguments really correspond to reality: rebels intelligent enough to consider the long-term consequences of their actions are unlikely to realistically expect that they will be successful in overthrowing a modern, established nation, and ones who lack that foresight aren't likely to drop all their plans just because they fear they may someday get the chair. Plus, rebels who do expect to be liberated as heroes in the foreseeable future have little to fear considering how many years of appeals there are before the actual execution. But even if I concede to you that the death penalty might in some rare, select instances help deter potential rebels, you don't address the danger of using the death penalty in such cases: we risk turning the attackers into martyrs, thus adding fuel to the fire of their cause. In the long run, if we truly care about peace and stability, we should treat such people humanely in order to maintain the moral high ground. By doing so, we take the wind out of our enemies' sails, dismantle their attempts to portray us as evil, murderous, unjust, etc. Whether a few imprisoned individuals live or die hardly matters in the grand scheme of things; what matters more is for the state to maintain its just, compassionate image in order to nip hostile sentiment in the bud and prevent future coup attempts. Promoting fear through execution will merely promote more hate in the long run.