I want to make clear my position on torture based on my reading of the months of discourse on St. Blogs regarding the topic. Before all of this came up Mark Shea was very correct in assuming my mindset on the topic.

Most Catholics never give the question of torture a thought, I'll wager, so their easy assumption that "It's probably okay sometimes: you know, to save New York and stuff" (source)

From a Catholic perspective the papal encyclical Veritas Splendor provides the key text in discussing this issue.

These are the acts which, in the Church's moral tradition, have been termed "intrinsically evil" (intrinsece malum): they are such always and per se, in other words, on account of their very object, and quite apart from the ulterior intentions of the one acting and the circumstances. Consequently, without in the least denying the influence on morality exercised by circumstances and especially by intentions, the Church teaches that "there exist acts which per se and in themselves, independently of circumstances, are always seriously wrong by reason of their object".131 The Second Vatican Council itself, in discussing the respect due to the human person, gives a number of examples of such acts: "Whatever is hostile to life itself, such as any kind of homicide, genocide, abortion, euthanasia and voluntary suicide; whatever violates the integrity of the human person, such as mutilation, physical and mental torture and attempts to coerce the spirit; whatever is offensive to human dignity, such as subhuman living conditions, arbitrary imprisonment, deportation, slavery, prostitution and trafficking in women and children; degrading conditions of work which treat labourers as mere instruments of profit, and not as free responsible persons: all these and the like are a disgrace, and so long as they infect human civilization they contaminate those who inflict them more than those who suffer injustice, and they are a negation of the honour due to the Creator"

The quote from Vatican II is from Gaudium et Spes.

Also CCC 2297

Torture which uses physical or moral violence to extract confessions, punish the guilty, frighten opponents, or satisfy hatred is contrary to respect for the person and for human dignity.(source)

Jeff Miller over at the Curt Jester summarized well in a comment on the CMR blog

The heavy lifting on this subject has been done by Mark Shea, Zippy, and Tom at Disputations. The short take is torture is an intrinsic evil and we can never do evil to do good. It is certainly the case the the magisterium and the papal magisterium in particular is teaching this as evidenced by the Catechsim and Vertitatis Splendor.

Too often torture apologists start by imitating Pontius Pilot and saying "What is torture" and then go to a specific situation such as the ticking bomb scenario. Using this scenario to make torture sound reasonable does not address the morality of torture. (source)

I firmly side with the stance that the question "What is torture?" is a sideshow to the real issue.

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So lets review:
In Romans 3:8 St. Paul clearly states that those who argue "let us do evil that good may result" deserve condemnation.
Torture is intrinsically evil.

But still, people insist on the definition of torture. To me the definition of torture is self evident but a satisfying take was published by The Public Discourse in an essay "Torture, What it is, and Why it is Wrong."

Its conclusion was as follows:

Yet taken en masse, the range of enhanced interrogation techniques looks very much like a strategy for breaking down hardened characters bit by bit; standing naked, shackled, deprived of sleep, kept awake with cold water and loud noise, prevented from cleaning oneself after defecation, and subject to painful (though not physically damaging) slaps and disorienting smacks against a wall—and then subject to repeated waterboarding over a course of weeks or months: this looks like precisely the sort of choice described by Lee and myself (though I do not, of course, speak for Lee in drawing my conclusions), viz., the choice to disrupt an agent’s capacities for personal integrity by disrupting his control over his emotions, choices, self-awareness and self-image, connection to other human beings, and judgments.

If so, then neither legal distinctions between this and the infliction of severe pain and suffering, nor consequentialist judgments about national security, nor even reasonable awareness that these terrorists were bad people, and that the US was in a very difficult situation, making hard choices under considerable stress with, in most cases, the good of the country in view, should obscure the judgment that these approaches involved torture. This judgment should especially guide us in going forward: we should repudiate such techniques across all intelligence gathering operations, as was done in the Army Field Manual for Human Intelligence Collector Operations and resolve to hold such operations to the highest moral standards. But we should hope that such a resolve is possible without descent into the politicizing and partisanship that threatens to knock any effort at serious moral self-criticism off course.

The problem is, I suspect, is that the partisanship is really what stands in the way.

I find it very difficult to understand the reasoning that calling torture a rose makes it any less torture. "Let us do evil that good may result". Feel free to tread there. But do so at the risk St. Paul mentioned.