Mith,
Hi there.
I agree, but what is meant by "internal intention"? Intention signifies end of an action. I think Lad's position is that it doesn't matter what a priest or person believes about what is being done, but that he intends to do it, i.e. the action. A priest who doesn't believe, for example, in transubstantiation, is nonetheless intending to perform the sacramental act of consecration by following the prescribed words and offering the host to the faithful who approach him for it with the faith of the Church. Just as a heretic might not believe that baptism effects a spiritual regeneration might nonetheless intend to perform the rite of baptism prescribed by the Church to render baptism to someone who desires Catholic baptism with a Catholic faith at the time of death.
Lad is not disclaiming all intent, but subjective intent as to what is being done as irrelevant. The intent to do the act, presumed by the action done, is always necessary. His example of the kids playing at baptism is a good example: they only intend on playing priest, not conferring a sacrament of the church to someone coming to them for the sacrament. Whereas the non-believing priest intends to administer the sacrament to those who come to him, as the Church directs him to do - otherwise why would he do it? If he does it to maintain his position in the Church for whatever reason (to continue to receive food and board, to influence some away from the Church if they come to him for spiritual guidance, no matter - since he intends to do what the Church intends, which is necessary to remain as priest in the Church), he's doing it intending to do what the Church requires him to do to maintain his standing, etc.
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The necessary intention is to do what the Church does. It matters not one but what the minister believes, it matters that he (or even she) intend to do what the Church does.
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I have seen moral theologians specify even further what "the Church does" means, but those further specifications are just explanations that shed additional light on the psychology of the minister. The actual standard really is to just "do what the Church does." It's a pathetically low bar (fortunately!).
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A Jєωιѕн midwife who baptizes an infant with the intention to "do this thing Catholics do to their babies" satisfies the bar of intention. A Jєωιѕн actor who is baptizing an infant for a scene in a film (like in the famous Godfather assassination/baptism scene) intends to "do this thing that's in the script" does not have sufficient intention.