Eugene Volokh has been posting a lot about torture. Recently here, and a previous post here. He reviews some pro and con arguments, but ultimately does not (cannot?) decide.
Some comments on his arguments, first. Volokh writes: "constitutionalism and the rule of law, I think, are generally good ideologies". Yes. Given that torture is cruel almost by definition, how can it possibly be justified while the eighth amendment stands? I don't think it can. But then I am one of those people capable of reading the second amendment as guaranteeing a right to possess and carry around guns.
Of course, original intent is not an argument against torture per se. It's just an argument that torture is not compatible with the words on a particular piece of paper. If torture is really worthwhile, then we should amend the constitution to allow it. So the other arguments Volokh makes must be pondered seriously.
On risks, I agree with Volokh that the slippery slope applies to torture in a big way. But Volokh is willing to consider playing around at the top of that slope; I'm not. Even 100000 lives saved when a nuke is revealed pale in comparison to the lives at risk if this society turns repressive.
Alternatively, we might keep torture illegal but sometimes do it anyway. Volokh is unsatisfied with that line of argument: won't it result in contempt for constitutionalism? No, I don't think so. For one thing, in any instance of torture it is unlikely to be clear whether or not it actually proved useful. Might the bomb have been found some other way? Was the bomb actually constructed properly? When would it actually have gone off, and how many might have been killed? Etc. Second, even given clear evidence that lives were saved, it will be unclear that torture is something anyone should do. Even people that believe that in some particular instance torture paid off, should be uncomfortable with the torture itself. There will never be a push to "rationalize" it with the 5th amendment. And therefore I don't think the damage to constitutionalism will be more than trivial. (Certainly, the recent Supreme Court selection of the president caused much greater damage.)
Now, the arguments above are but responses to Volokh. But here's a new question: why torture at all? Why now? The answer is, of course, "terrorism". But why can't we just live in peace? The answer lies in part with the terrorists -- they don't like our culture for reasons we won't control, like say Britney's belly. But it lies in part with us -- we are trying to run the world, including most particularly helping despots rule Islam. Ideologically, America holds out hope of a better world -- self determination of peoples; rule by consent of the governed. But we give the lie to our own words, supporting dictators like the Shah, Saddam Hussein, the Saudis, Arafat, Musharraf. This has gone on for 50 years, and the people there are not blind. They know that the USA is their enemy, when it should be their friend. That's why some of their anger gets directed at Americans.
The solution is simple. America should stop supporting dictators, and stop using power to push other people around. We should pull out of Saudi controlled Arabia - let Saddam attack 'em; I don't care. We should stop the embargo against Iraq. We should cease all military sales to Israel, and convert our $4b/year to Israel into a program to buy out West Bank settlers. We should arm-twist Israel into unilateral separation from Palestine, guaranteeing their survival during the transition with our military but no longer supplying them anything for day to day use against Palestinians. (Israel is beginning to do this anyway, no thanks to the USA.)
If we were to do these things in the Middle East (and similarly stop pushing around people elsewhere), a wonderful thing would happen. Instead of being looked with a mixture of love, hate, envy, and annoyance by the world, we would be ignored. Over time even the radical islamicists would stop worrying about us, and turn their anger instead where it belongs -- against their own oppressive governments. Then, as in Iran, they will have revolutions, and turn into even worse theocratic nightmares for a while. And then, as revolutions do, they will moderate. And finally Islamic democracy will result.
The logic of repression is gradualist. You oppress a little; a reaction happens; you oppress a little more. You send in troops, force a boycott, get more police, build more prisons. People are hurt by it; the oppression is obvious and fringe lunatics take up arms. That's when you end up talking about torture. It's yet another control oriented fix for deeper social problems, all originating in the actions of the state. The solution is not more and more harshness, but to stop the state from doing what it should not have been doing in the first place.