In this morning's thread [September 4], there are two entries which express the common mistake that the 'intention' a minister needs to have is something which must include a correct orthodox doctrine of the Sacrament ("If a Bishop doesn't believe in Sacrificing priests, how can he intend to ordain them?"). This error is so grave (you'd never know for sure whether any sacrament was valid because you could never be sure that the bishop's or priest's views were orthodox) that I have, below, wearied the patience of regular and long-time readers by reproducing posts dating from 2010 9 August, 2013 21 November, 2014 1 March.
PS There is far too much of the waspish schoolmaster in me ... which is why I have, I am afraid, been refusing comments from those who, it seems to me, have simply not read the three old pieces I reproduced yesterday. There is, of course, no reason why anybody should read anything I write. But if you decline to do so and then write comments, there is no reason why I should consider them useful contributions.
I don't see how I can express myself any more clearly than I have, more than three times now, attempted to. But one last try ...
Simple rule: (1) If someone says that a Sacrament is invalid and that this invalidity results simply and solely from some mistake, or some heresy, in the mind of the Minister, then he is wrong. This is contrary to the Church's teaching.
(2) If, however, someone says that, because of his mistake or heresy, the Minister used Form [words] or Matter [physical things or actions] which are not adequate to convey the Sacrament [this was the argument in Leo XIII's bull Apostolicae curae], then Catholics can discuss in detail about the adequacy of the Form and Matter which the silly fellow did use.
This discussion might lead to all competent people being 100% sure that what he did was inadequate; in which case the Sacrament must be repeated absolutely. If, on the other hand, competent people disagree or entertain differing degrees of probability, then the Sacrament is to be considered doubtfully conveyed and should be administered conditionally.
If the Magisterium gives a ruling, that, while not being infallible in terms of Pastor aeternus of Vatican I, provides a judgement which should in practice be followed because Sacramental validity matters.