[Question:]{.underline} Can I confess as sins actions or words that I did not realize were sinful at the time I did them?
[Answer:]{.underline} This question concerns the remote matter of the sacrament of penance, namely the sins that are to be confessed. This is necessary matter, that must be confessed, if it concerns mortal sins committed after baptism, which have not yet been confessed. It is free matter, that may be confessed, but which does not have to be confessed, if it concerns venial sins committed after baptism, or any sins that have already been absolved in the sacrament of penance.
However, a further distinction has to be made, namely between certain and doubtful matter for the sacrament of penance. Sins are doubtful matter if it is not certain that there was culpability at the time the acts were committed. This is the case in question here. This can happen if a person had an erroneous conscience, that is when he did not realize the moral evil of what he was doing, such as dressing immodestly in public, or watching suggestive movies. Now that he understands the evil of such actions he regrets them and wants to confess them, but since he did not understand at the time that they were certainly evil, they are doubtful matter. The other frequent case of doubtful matter is when there is a doubt as to the consent given, as in the case of impure thoughts or sudden movements of anger. In these cases, likewise, there is real regret and the desire to confess what is now perceived as having been disordered and is known to have been wrong. Can such sins, that are doubtful matter, and which are certainly very frequent, be confessed?
In order to resolve this question, a further distinction is made, namely between sufficient and insufficient matter. Sufficient matter is that which suffices to receive a valid sacramental absolution. Only certain matter is sufficient for a valid sacrament, whether it be necessary matter (= unconfessed mortal sins) or free matter (= confessed mortal sins and all venial sins), as is stated in Canon 902 (1917 Code). Doubtful matter is insufficient matter, not because there is an absence of culpability, but because the confessor cannot judge with certainty of the culpability and grant his absolution of it. It is for this reason that there is no strict obligation of confessing even mortal sins if there is a real doubt as to the awareness of the culpability at the time (Council of Trent, Db 899 & Prummer, Man. Th. Mor. III, §375).
However, this does not mean that doubtful matter cannot be confessed. The penitent can be very much aware of the culpability of his actions, and yet for the confessor it is objectively doubtful matter. He may not have been fully aware of the culpability of his actions at the time, but this does not at all mean that he does not have any culpability at all. Far from it, how frequently it happens that our ignorance is at least partially culpable. Likewise, we understand the culpability of those immediate actions, for which there is not sufficient reflection to constitute certain matter. Yet, it is our fault if we get angry, or make some spiteful remark, or act with impetuosity, and we could and should have avoided it. Must these obviously culpable acts not be confessed simply because they do not constitute certain matter for the Confessor?
It is certainly true that such indeliberate venial sins, or material sins (whose culpability was not known at the time) do not alone constitute sufficient matter, and that if they alone were confessed, the confessor would have to refuse absolution, rather than to give an invalid sacrament, due to lack of sufficient matter. However, this does not mean that they cannot be confessed. They certainly can be confessed if they are combined with other sins, which are certain matter. These can be deliberate sins committed since one’s last confession, or already confessed sins from one’s past life. If they are mentioned the confession is certainly valid, and the absolution will also include the culpability, clear to the penitent, but doubtful to the confessor, of other indeliberate sins that do not constitute necessary matter. Hence the importance for those who go regularly to confession to always mention, at least in general, a sin from one’s past life. With these they can confess all their imperfections, and receive the grace of the sacrament, the absolution and the spiritual direction of the priest to overcome them. More than this, they in fact should confess such imperfections, if they want their frequent confessions to help them to overcome their faults and strive for perfection. This is the correct use of the sacrament of penance by those who desire to go to Confession regularly, as they Church recommends.
This is the clear teaching of Father Prummer, Op. Cit. §324:
“By imperfections in this subject are to be understood those acts which are less good, which objectively speaking do not constitute a certain transgression of the eternal law. Since, indeed, such acts individually considered cannot be indifferent, such aforesaid imperfections are in reality either good or bad acts; but since the confessor cannot ordinarily judge with certainty of their sinfulness, they are not sufficient matter for absolution. Thus, for example, those who accuse themselves of having omitted their morning prayers, or of having had involuntary distractions in prayer, or having suffered sudden and involuntary movements of anger or of concupiscence, bring insufficient matter for sacramental absolution. But such penitents can praiseworthily declare such imperfections [in confession] in order that the confessor might judge better of the state of their soul, and give good counsels, but they are greatly to be encouraged that in addition to these imperfections, they at least confess some sin of their past life…”
Answered by Father Peter Scott, SSPX.