Moral theology

(a) They are materially evil in themselves and formally evil in their cause. Example: Titus, who intends to take a position in which he will have to advise others, foresees that later on he may make mistakes costly to others, as a result of his present lack of sufficient study. He secures the position, and tries to make up for former neglect of study, but on one occasion injures a patron by wrong advice which he would not have given, had he worked more faithfully as a younger student. The wrong advice is objectively sinful in itself, as being an injury; it is subjectively sinful in its cause, as being the result of negligence which foresaw what might happen.

(b) The acts in question are not formally evil in themselves. Example: Titus was formally guilty of injury to others at the time he foresaw what would happen on account of his negligence; he was not formally guilty at the time he did the injury, because he had tried meanwhile to repair his negligence and was not conscious of his ignorance.

(a) Sin committed by following a vincibly erroneous conscience is of the same gravity and species as the act for which the conscience is responsible, but the ignorance is an extenuating circumstance. Example: He who blinds his conscience so that it decides in favor of grave calumny, is guilty of mortal sin against justice; but he is less guilty than if he had sinned without any permission from conscience.

(b) Sin committed by disobeying an invincibly erroneous conscience is of the gravity and species apprehended by the conscience. Example: A person who tells a small lie, thinking it a mortal sin against charity, is guilty of the malice he understands to be in his act.

(c) Sin committed by disobeying a vincibly erroneous conscience is of the species that was perceived. Example: Caius who did not live up to his promise of telling a lie, after he had decided that to keep his word was the right thing to do, was guilty of a breach of promise. As to the gravity of sin against a vincibly erroneous conscience, it is always the same as that apprehended by the conscience, unless what is seriously wrong is culpably mistaken for what is only slightly wrong. Examples: If Caius, just referred to, thought that his desertion of his friend inflicted a grave injury, he was guilty of grave sin. A person who persuades himself by vain reasonings that complete intoxication does not differ in gravity from incipient intoxication, is nevertheless guilty of the greater malice, if he puts himself in the former state; for his wrong opinion cannot change the fact, and his culpable ignorance cannot excuse him.

(a) If the species of evil is not determinate before the conscience, but an indifferent act is thought to be sinful without any definite species of sin being thought of, he who acts against such a conscience seems to commit a sin of disobedience. Example: A person who thinks that smoking is a sin, of what kind he does not know, must have at least vaguely the opinion that it is forbidden by the divine law; and hence, if he smokes, he is guilty of disobedience.

(b) If the gravity of the putative sin is not determinate before the conscience, but an act is thought to be sinful without the degree of sinfulness being at all known or thought of, he who acts against such a conscience commits a mortal or a venial sin according to his own disposition with respect to sin. If he is so attached to the sin he apprehends that he intends to commit it, whether it be great or small, he is guilty of mortal sin, at least in so far as he exposes himself to it. But if he is habitually resolved not to commit grave sin, it can be presumed that he would not do that which he apprehends as sinful, if he thought it was a grave offense, Example: If a person erroneously thinks that it is a sin to read a certain book, and then reads it without adverting at all to the gravity of the sin he apprehends, his greater or less guilt will have to be judged by his character. If he is so conscientious that he would stop reading at once if he feared the book was seriously harmful, he sins only venially; but if he knows that he is lax and is yet resolved to read the book at all costs, it seems that he is guilty of grave sin.