A while back I wrote two articles on the validity of Protestant baptisms. The first of these wound up being cross-posted at Called to Communion and generated some controversy even among Catholics, which (to be honest) was disappointing. Now I have the opportunity to add to what I have written. I have been reading St. Francis de Sales’ masterpiece The Catholic Controversy, and I happened to stumble across the following on the subject of Baptism. The book is simply excellent as an apologetics resource, and frankly it surprises me that it is not more readily available.
But I digress. Quoth the Saint:
The Council [of Trent] does not say that it is necessary to have the particular intention of the Church (for otherwise Calvinists, who have no intention in Baptism of taking away original sin, would not baptize rightly since the Church has that intention) but only the intention of doing in general what the Church does when she baptizes, without particularizing or determining the what or the how.
Again, the Council does not say that it is necessary to mean to do what the Church of Rome does, but only in general what the Church does, without particularizing which is the true Church. Yea if a man, thinking that the pretended Church of Geneva was the true Church, should limit his intention to the intention of the Church of Geneva, he would indeed be in error if ever man was in error, in his knowledge of the true Church, but his intention would be sufficient in this point, since, although it would point to the idea of a counterfeit Church, still it would only have its real significance in the idea of the true Church, and the error would only be material, not, as our Doctors say, formal.
Further, it is not required that we have this intention actually, when we confer the Sacrament, but it is enough that we can say with truth that we are performing such and such ceremony, and saying such and such word, as pouring water, saying, I baptize thee in the name of the Father, and so on—with the intention of doing what true Christians do, and what Our Lord has commanded, although at the moment we may not be attentive to this or thinking of it. [The Catholic Controversy, Part III, Article I, Chapter III; I do not know if it is available for reading online, but it is available for free download here]
In short, St. Francis confirms what I wrote previously: the presumption of the Church is that Protestant baptisms are valid. And he cannot be written off as a “modernizer”—neither by Catholic traditionalists nor by Protestants with a chip on their shoulder who insist (without warrant) upon being treated as “damned” by Trent: He wrote the book less than a century after the Council of Trent and was proclaimed a Doctor of the Church in 1877.
Aquinas, Etc. 
I agree that Protestant baptisms are valid, but I have a question about how you interpret St Thomas Aquinas in ST 3:68:8 (http://www.newadvent.org/summa/4068.htm#article8)
This seems that there are at least some times when a person lacks the right/required faith and thus even though he receives baptism is it “not unto salvation”. The question is, what are the conditions to not receive the baptismal graces? How willfully in denial must a person be?
Hi Nick,
I reckon we can draw at least some guidance from the validity of infant baptisms. My thought would be that a person must formally disbelieve, not merely materially, since many Catholics materially disbelieve articles of faith which they would embrace if properly catechized. For example there are already defects if the Sacrament is not administered by a priest, but this is not sufficient to invalidate it.
Lastly, I think St. Francis sets the right tone when he says (as quoted above):
So in similar fashion if the one being baptized as a Protestant has the intention of believing what (so far as he knows) is the true teaching of God, this would be sufficient to validate his baptism.
Fred