Jimmy Akin has written some postings (here, here, and here) in an attempt to narrow down what 'torture' might mean when it was condemned as an intrinsic evil by Vatican II and Pope John Paul II. I think his reflections are interesting, but often as much off-course as on-course.

For example, he proposes two parameters to guide the process of coming up with a definition:

Parameter 1: The definition should correspond as much as possible to our pre-reflective sense of what constitutes torture.

I'm very dubious about that. Our human pre-reflective sense can be extremely muddled, and it is necessary to dissect that muddle, and drop out what is not useful (and what is dropped may be a little, or a lot).

Parameter 2: The definition should point to something that is intrinsically evil.

Whatever the Council and Pope had in mind for what was intrinsically evil, they clearly had something in mind, and not vague generalities. One part of a relevant quote from the Council and Pope is where it includes torture in a list of those things which:

violates the integrity of the human person

and that statement provides a strong clue to what it was that led to this kind of torture being an intrinsic evil.

Then Akin jumps ahead by more than a few steps, and says:

The fact that Church authorities once used torture, in keeping with the legal custom of the day in secular society, is a matter of intense shame.

As I have previously pointed out, I would like to wait to see exactly what 'torture' is defined as before trying to apply it to a previous historical situation. (Part of reducing the muddle.)

Akin proposes the following as a definition of torture:

The sin of torture consists in the disproportionate infliction of pain.

And I think that a definition like that can never help elucidate what must be an intrinsic evil. Firstly, it leaves undefined exactly what kind of proportionate comparison is proposed. And secondly, any proposed scale of pain leaves it necessarily vague as to who is to decide that counts as too much pain. Different people feel pain differently. What is too much for one is not for another. But then defining 'torture' in that way would necessarily be a subjective thing, and thus could not possibly be intrinsic. Nor, alternately,  could we leave it up to a social consensus, or a vote, as to what was to be counted as too much pain, since that would still be subjective. But the Church is condemning something as intrinsically wrong.

Akin also misses the Church's condemnation (directly adjacent to the condemnation of mental and physical torture) of attempts to coerce the spirit – which can be regarded as the spiritual form of torture. This means that the torture of an Islamic terrorist to find out about a ticking bomb (the explosion of which the terrorist regards, however mistakenly,  as a morally correct action) is an attempt to coerce the spirit, and thus also intrinsically wrong.