The Claudy bombings were a disgraceful episode in a disgraceful history of murder and terror but one doubts whether we are really any nearer the truth concerning the involvement of individuals. Was Fr James Chesney involved in the bombing or not? All decent-minded people must be disgusted at the thought that he might have been; they must also be disgusted at the thought that he is being talked and written about as guilty when we don't actually know. The fact that he's dead adds to the unease: he cannot defend himself.

When we move from the particular (Fr Chesney) to the general (Catholic Church), the situation becomes more complicated, because the Church exists here and now; but while the Church of the day is often held to account for the faults and failures of the Church of the past, the historian in me questions whether that is always valid. For example, I, personally, feel no need to "apologize" for the excesses of various Inquisitions, much as I abominate what was done. In fact, it's quite likely that my ancestors were both persecuting and persecuted; the same is probably true for most people. But historical apologies of that kind have become fashionable, indeed are often demanded. Any moment now I expect to read a demand for an apology "from the Church" for the evils Fr Chesney is suspected of having committed. I'm not sure how that works.

It is always easier to make accusations of conspiracy and cover-up than to substantiate or rebut them. The trouble is, accusations about conduct in the past tend to colour people's views of the present: ask anyone with the surname of Borgia or Crippen. So, the discussion about the Claudy bombings has implications for the present, even if we can never reach certainty one way or the other about Fr Chesney's involvement.

The difficulty of establishing facts and of judging them (not the same thing, although often equated) is compounded by the difficulty of making an imaginative leap into the world of the past, of entering into how people thought and felt about things in days gone by. People laugh now when I recall that my father told me, in all seriousness, never to go out with a man who wore a made-up bow-tie. It was code, of course, but a code we all understood. No one understands the code today: we think it just plain silly. Was it silly at the time? It didn't seem so.

Similarly, can we enter into how politicians and clergy thought and felt about the IRA and the "structures of society" forty years ago? It's difficult, even for those of us who lived through those times. It might be more helpful to concentrate on what is very much a question of our time: the need, real or imagined, to apportion blame, to make someone pay for wrongs done. The enormities of the Pol Pot regime and the Lockerbie bomber spring to mind, and the debate about how justice should be served. No one is arguing that wrong-doing should go unpunished, it's more a question of deciding what is appropriate punishment, what other factors should be taken into account beyond the establishment of guilt.

It may sound lame, but maybe we should just concentrate on trying to keep society safe now, leaving the evils of the past to God. "Vengeance is mine, says the Lord." It is better left to his hands than ours.