Section — Slater, Manual of Moral Theology
Section III. The Confessor as Counsellor
The duties of the confessor require considerable expert knowledge in one who aspires to the office. He must in the first place have a competent knowledge of Christian morals and of all that belongs to the valid and lawful administration and reception of the sacraments. St Alphonsus teaches us that it is not sufficient merely to know the general principles of Christian morality; the confessor must have considerable skill in applying those principles correctly, according to the infinite variety which is found in human actions. The confessor should have received a thorough grounding in moral theology during the course of his priestly studies, and he should continue to keep it up during the rest of his life, for it is quickly lost unless means are taken to keep it fresh in the mind. The Church shows that she is conscious of this danger by insisting that all who have the cure of souls should at certain times every year be present at the conferences of the clergy, where moral questions are discussed. Every confessor is not called upon to be an authority in moral questions, but at least he should be able to decide correctly ordinary doubts and difficulties, and know when to doubt about more serious questions.
p. ii, 168
The confessor is bound to instruct a penitent before he can give him absolution when he finds that he is ignorant of what he must know in order to receive the sacrament of Penance validly and lawfully. And so if the penitent does not know how to make an integral confession, or how to make an act of contrition, the confessor must instruct him. In the same way, he must teach one who is ignorant of those truths which must be believed in order to be saved. Innocent XI condemned the proposition that a man is capable of receiving absolution however great may be his ignorance of the mysteries of the Faith, and even if through culpable negligence he does not know of the mystery of the most blessed Trinity and of the Incarnation of our Lord Jesus Christ. Ignorance of those Christian truths whose knowledge is required by precept, and of the obligations of one’s state of life, is not a bar to valid absolution, and in spite of it absolution may lawfully be given on condition that the penitent undertake to learn what he should know, if the confessor cannot give the necessary instruction at once.
p. ii, 169
No general rule can be laid down as to whether the confessor should instruct a penitent whom he finds to be ignorant on other matters. Various cases must be distinguished. If the ignorance of the penitent is morally hurtful to him, as is an erroneous conscience which thinks that a perfectly harmless act is sinful, the confessor should put his conscience right. Again, if the penitent asks whether an action is lawful or not, the confessor should instruct him. In other cases, if the penitent is ignorant of his obligation, and he would not fulfil it even if he were told, as a general rule the confessor may and should abstain from telling him under the circumstances. For the information would do no good, but only harm, inasmuch as the sins which hitherto were only material would henceforth be formal. 'There is, however, an exception to this rule when what is done in ignorance and good faith is a cause of public scandal, for then the public good requires that the penitent should be told even to his temporary private loss.
On these principles authors agree that if a confessor detect a diriment impediment between parties who think that they. are validly married, he should not inform them of it, at any rate until he has obtained the necessary dispensation, so that he can at once proceed to set the matter right.
Section Iv e e 2 The Confessor as Fudge
p. ii, 169–170