[Question:]{.underline} Before Vatican II, did the Church accept Protestant baptisms?
[Answer:]{.underline} Already in the 3^rd^ century, the Church defined that the fact that it is a heretic who administers the sacrament of baptism does not make it invalid (Dz 110). The baptisms of Protestants are consequently to be considered valid, unless a reasonable and prudent doubt occurs as to a defect of the required matter, form or intention. (Cf. Roman Ritual, Titulus II, Caput 3, §11 & 12). If there is certitude about the validity of the Protestant baptism, then there is no need to repeat the administration of the sacrament. The ceremonies are to be supplied, the convert makes a general confession, a profession of Faith and abjuration of heresy, and the excommunication incurred is lifted.
However, the usual situation is that it is practically impossible to prove the validity of the Protestant baptism. Since the investigation is very difficult to do and the validity of the Protestant baptism practically impossible to establish, the custom before Vatican II was to baptize conditionally practically every convert being received into the Church. This is still the practice of traditional priests, who are aware of their obligation to guarantee with certainty the validity of the sacrament. This does not mean that the validity of Protestant baptisms is denied, but simply that they do not have the certitude necessary for a sacrament so necessary for the salvation of souls.
Answered by Father Peter Scott, SSPX.