I disagree, and so does St. Thomas. It's based on the objective and externally-manifested (albeit internal) intention of the minister. So if the priest performs the Catholic Rite as prescribed, he has the intention to do WHAT the Church DOES ...
A priest who forms a contrary internal intention does not confect the sacrament, despite the performance of the external rite.
Generally speaking, we are morally certain that a priest who performs a sacramental rite (e.g., TLM or NOM) possesses sufficient intention, because there can only be positive doubt regarding a contrary intention if it is manifested somehow in the external forum.
But this is not the case in Fr. Scott's argument:
He is not concerned about what is being externally manifested, but in what is NOT being externally manifested.
By definition, this can only produce a negative doubt, since, there being no external manifestation of a contrary intention, the consideration pertains to the internal forum (which is unknowable without such external manifestation).
In short, the requisite intention, which is nearly automatic (and not on the basis of the form of the rite, but on the basis of a sane priest performing a sacramental rite obviously aware of doing what the Church does) is so difficult to lose
, that doubting its presence without any manifestation of having formed a contrary intention, is practically inadmissible.
Here, once again, is Fortesque:
“People who are not theologians never seem to understand how little intention is wanted for a sacrament… The ‘implicit intention of doing what Christ instituted’ means so vague and small a thing that one can hardly help having it — unless one deliberately excludes it. At the time when everyone was talking about Anglican orders, numbers of Catholics confused intention with faith. Faith is not wanted. It is heresy to say that it is. (This was the error of St Cyprian and Firmilian against which Pope Stephen I [254–257] protested.) A man may have utterly wrong, heretical and blasphemous views about a sacrament and yet confer or receive it quite validly.”
-Adrian Fortescue: The Greek Fathers