Those who defend torture normally do so on consequentialist grounds. They posit cases such as the “ticking time bomb” in which the harm done by torture is insignificant compared to the good it does. The consequences of torture are clearly beneficial, overall: OK, it does some harm to an individual terrorist who has hidden the bomb but at the same time it saves thousands or millions of lives. When so many lives are at stake, a utilitarian calculus will clearly show that the good that will follow from torture outweighs the good that will follow from the refusal to torture.
Usually, we see a kind of threshold consequentialism rather than a pure consequentialism at work in such arguments: if torture can produce one more unit of “utility” (wellbeing, life, etc.) than the refusal to torture, most consequentialists wouldn’t allow torture. The good consequences of torture must far outweigh rather than marginally outweigh the harm it clearly does. Hence the hypotheticals in examples such as the ticking bomb, in which it’s posited that very many lives are at stake. We are allowed to supersede the deontological rule that one shouldn’t torture only beyond a certain threshold of harmful consequences that would result from sticking to the rule. As someone has said, lost lives hurt a lot more than bent principles. Strict moral absolutism, whatever the possible consequences, can indeed land you in all sorts of problems.
However, let’s look a bit closer at this seemingly convincing argument. We can overlook some of the possible difficulties and still conclude that the argument is unsatisfactory. Let’s not dwell on the likelihood that in real cases, the numbers of possible terrorist victims is rather small, while the number of people who have to be tortured is probably higher than one: you may need to torture some people before you find the one who has the necessary information about the location of the bomb; then you may need to torture his friends and family because he’s trained to resist torture and because he knows that if he resists for a short time, the bomb will go off. So let’s forget that the utilitarian calculus will most likely be less unequivocal than assumed in the argument above: we’ll never or only very rarely have cases in which torture produces a very small harm and at the same time a very large benefit. The harm and benefit will be much closer to each other.
Let’s also not dwell on the fact that the greater good thinking of the argument puts the torturer on the same footing as the terrorist. The latter also assumes that he fights for a greater good and that the harm he does is small compared to the benefits this harm will produce. The similarity between torturer and terrorist is all the more striking if the torturer has convinced himself that it’s necessary to torture the innocent (when the terrorist himself doesn’t speak fast enough). Putting ourselves on the same level as terrorists means giving up our identity to save ourselves, which really is pointless. If that is correct then we have to remodel the utilitarian calculus: the harm done by self-destruction is probably greater than the suffering caused by exceptional terrorists attacks. So even the utilitarianism of the greater good doesn’t justify torture.
But let’s assume that none of this speaks against the standard consequentialist justification of torture and that we manage to use torture in a way that saves many many lives, that doesn’t impose a high cost, and that doesn’t put us on the same level as the terrorists. So we can save ourselves, our identity and the lives of many of our fellow citizens. Still, the “good” that we achieve through torture is tainted by the methods necessary to achieve it. The notion, inherent in the consequentialist justification of torture, that certain goods can be attainted by problematic means, is itself problematic. We can save ourselves, but once we are saved we believe that our success has been tainted by the immoral methods used to achieve it. We may not be willing to enjoy this success and the goods we have if they have been secured by way of torture.
Jeremy Waldron has interesting things to say about tainted goods. Read this for example.