The Catechism of Pope Saint Pius X is not infallible. It is generally a reliable source of doctrine, as are other catechisms approved by the Church. But it can err, at least to a limited extent. It seems unlikely there are any grave errors in that Catechism, but the Church might define a new definition of dogma, in the future, that would necessitate revision of one or more Answers in that Catechism (or any Catechism).
On baptism and mortal sin
14. Q. When the person who is being baptised is an adult, what dispositions should he have?
A. An adult who is being baptised, besides faith, should have at least imperfect contrition for the mortal sins he may have committed.
15. Q. If an adult in mortal sin was baptised without such sorrow, what would he receive?
A. If an adult was baptised in mortal sin without such sorrow he would receive the character of Baptism, but not the remission of his sins nor sanctifying grace. And these two effects would be suspended, until the obstacle is removed by perfect contrition or by the sacrament of Penance.
The Sacrament of Baptism, as well as the baptism of blood and the baptism of desire, infuses the three theological virtues of love, faith, and hope along with sanctifying grace. Now an adult preparing for baptism with water may receive the baptism of desire prior to the formal Sacrament of Baptism, as Saint Thomas Aquinas notes. In that case, the candidate will already have love, faith, and hope with sanctifying grace, since the time of his reception of the baptism of desire. A baptism of blood or a baptism of desire also confers forgiveness for all sins. So in that case, the candidate will receive, at the Sacrament of Baptism, in addition, the character and the complete remission of all punishment due.
Regarding Question 14, the candidate for Baptism can only have faith prior to baptism, if he has received a baptism of desire. This is the best case and is perhaps common, as those adults who sincerely prepare for Baptism will desire baptism perhaps sufficiently well before the eyes of God to receive a baptism of desire and will therefore have love, faith, and hope prior to the Baptism with water.
However, it is not required of an adult who receives the Sacrament of Baptism to receive first the baptism of desire. And we have no certain way of knowing if that baptism of desire was received first in any case. So faith is not required in order to receive that Baptism which confers love, faith, and hope.
Regarding mortal sins, baptism forgives all sin; baptism with water, the baptism of blood, and the baptism of desire each forgive all sins. Only the Sacrament forgives all temporal punishment due, necessarily, though the baptism of desire and the baptism of blood, being often preceded by virtuous acts of cooperation with grace, obtain the remission of some punishment, as is the case for the faithful who act with virtue.
That a candidate should have at least imperfect contrition is certainly true; he ought to have it. If he has perfect contrition, he receives by the contrition or he previously received a baptism of desire. And that baptism forgives all sins, so that he will not have mortal sins on his conscience at the Baptism with water.
What if a candidate for Baptism has imperfect contrition? The baptism forgives all his sins.
What if a candidate for Baptism has no imperfect contrition, but he sincerely desires to be Baptized into the Faith? Such a desire constitutes at least implicit imperfect contrition, which is sufficient for the Baptism to forgive all his sins.
What if a candidate for Baptism does not sincerely desire Baptism? Perhaps he is only being baptized because the Christian society in which he lives requires it to receive every benefit of that society. It was alleged in past centuries, in Christian nations, that some non-Christians received baptism but did nothing to show that they were Christians; they only receive baptism for the societal and political benefits of being perceived to be a Christian. In such a case, the candidate does not receive anything. The adult being baptized must at least desire the Sacrament sincerely, even if very imperfectly. No Sacrament is valid without the intention to do what the Church does by the priest or in some cases by the recipient.
I don’t see how a situation could occur where a baptism would be valid, but the adult candidate would not have at least an imperfect desire to be baptized, which would then constitute implicit imperfect contrition. So there is not a case where an adult receives only the character, but not the remission of sins and the virtues of love, faith, and hope with sanctifying grace that the character indicates. And therefore reception of the Sacrament of Penance does not result in the penitent receiving what Baptism with water confers in a delayed fashion. One Sacrament cannot confer what belongs to a different Sacrament.
In addition, a person cannot receive the Sacrament of Penance unless they are baptized into the Church. But this baptism requires the initial forgiveness of all sins, including original sin and all personal sins. IF only the character of baptism were conferred, due to the unrepentant actual mortal sin of the candidate, then the Sacrament of Penance would not be valid, as the person did not die and rise with Christ in baptism, which is what causes the forgiveness of all sin. So again it is not possible for the substance of the Sacrament of Baptism — sanctifying grace with love, faith, and hope and the remission of all sin — to be absent while the character witnessing to that substance is present.
Edited to add this paragraph (14 June 2022): I certainly will accept whatever the Magisterium decides on this question. But I don’t see how we can say that anyone received the Sacrament of Baptism for the forgiveness of sins, but did not have their sins forgiven. The character of baptism indicates that the Sacrament was received.
What I’ve written above is my speculation on these points. See Dr. Fastiggi’s note below.
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