The following was condemned (Pope Alexander VIII, Decree of the Holy Office, December 7, 1690, Errors of the Jansenists):
1318 28. Baptism is valid when conferred by a minister who observes all the external rite and form of baptizing, but within his heart resolves, I do not intend what the Church does.
http://patristica.net/denzinger/
Consequently, the use of the proper form cannot be said to imply the proper intention or the validity of the baptism.
The problem becomes knowing what was in the "heart" of the one administering the sacrament. If we are to question what is in the heart of every person that administers a Catholic sacrament, then we can never really know which sacraments are validly administered.
Yes, that's the case. We can never really make sure. We're left to act on what's called moral certainty. We may detect problems which raise doubts and then flee such cases/situations, but on the other hand we can never make 100% sure that a particular sacrament was conferred validly.
But is that really a problem? We can never be sure we make it to heaven, anyway. So it's not really a problem. We can be 100% sure that God will make sure that the chosen few will get what they need.
It is still my understanding that validity is presumed in such cases. Perhaps someone else with more knowledge and training can chime in...perhaps Ladislaus?
Earlier in this thread you already more or less said it:
Yes, as long as the form and matter of a Catholic Rite was used, then correct intention is presumed.
And if the priest wasn't making jokes at the altar. And if he didn't brag about his recent masonic initiation last night at the local pub. And ...
And in the case of Mormon or Protestant baptisms the correct intention is not presumed. Especially in the case that Rome has not yet decreed any decision. In such cases, circuмstances have to be evaluated. And this traditionally has been done, first of all in cases where Rome had been silent about so far.
The problem is whether the New Paul VI Rites are Catholic.
They're not Catholic. The heretics replaced the received and approved rites. To even say that they're Catholic is to win an anathema.
As for your other question above, the docuмent you provided states that it was traditional practice that Mormon baptisms were considered valid by the Catholic Church. Was there a pre-VII magisterial docuмent on it? I don't believe so, but it appears that the traditional hierarchy never questioned them in the past...until the Vatican II sect questioned them. If we follow what the Vatican II sect proclaimed, that would mean that there were a number of Mormon converts to Catholicism that were never validly baptized....which would also mean that the Catholic Church allowed those souls to go to Hell.
You presuppose that all sacraments are valid as long as they've not been explicitly declared to be invalid by the Church of Rome. That's not how things work.
I think I'll stick with the traditional practice of the Catholic Church.
I recommend to stick with the magisterium, here with the Decree of the Holy Office of December 7, 1690. And not with a perceived or fictional "traditional practice".