Moral Theology. Charles J. Callan
But, though the law itself remains, there are cases in which non-observance of it is excused from guilt. These cases can be reduced to physical and moral impossibility.
(a) In cases of physical impossibility (i.e., when the powers requisite for observance are wanting), one is manifestly excused; for law is reasonable, and it is not reasonable to require impossibilities. Examples: Infants are not guilty of sin against the Natural Law, when they do not pray; for they lack the use of reason, which is presupposed by the notion of prayer. He who is unable to work is not obliged to earn support for relatives.
(b) In cases of moral impossibility (i.e., when a law cannot be kept without the infringement of a higher law or the loss of a higher good), one is also excused; for it is unreasonable to prefer the less to the more important. Example: Titus lends a revolver to Balbus. Later he asks that it be returned to him, as he wishes to kill himself. Now, property is less valuable than life, and hence Balbus is unable in this case to observe the law which requires that things borrowed must be returned.
318. Moral impossibility is also defined as the inability to observe the law without serious injury or loss to oneself or a third party. Serious injuries are such as deprive some one of great goods, such as the use of reason, life, knowledge, friendship, health, reputation, property. Serious losses are such as prevent one from obtaining notable goods, The following rules indicate when grave inconvenience excuses, and when it does not excuse, from the guilt arising from the non-observance of Natural Law:
(a) when the law is negative (i.e., prohibitory), no inconvenience excuses from sin; for that which is forbidden by the Natural Law is always morally evil, and hence more to be shunned than even the greatest physical evil, or death. Example: One is obliged, under grave or light sin, as the case may be, to forfeit all temporal goods rather than blaspheme, murder, lie, etc.;
(b) when the law is affirmative (or mandatory), an inconvenience which, all things considered, is really and relatively grave, excuses from sin; for that which is commanded by the Natural Law is not always morally obligatory, but only at the right time and in the right circumstances (see 371), and hence its omission is not always morally evil. Examples: Sempronius vowed that he would go on foot to a place of pilgrimage, but when the day came he had a sprained ankle that would be badly injured if he walked. Caius received a jewel stolen from Balbus and promised that he would return it at once to the owner, but he finds that he cannot do so now without danger, either of the arrest of himself or of the one who took the jewel. Titus sees a person who has been seriously injured lying by the roadside, but he is tired, and neither gives help himself nor summons aid. In the first two cases the inconvenience is grave, and hence Sempronius may ride to the place of pilgrimage, and Caius may return the jewel to Balbus later; but the inconvenience of Titus is slight, and does not excuse him from sin.
319. Just as the Natural Law is unchangeable, because based on the unchangeable Eternal Law instituting the nature of man, so is it easily knowable, because it is promulgated by the light of reason. Hence: (a) invincible ignorance of the entire Natural Law is impossible in any person who has the use of reason; (b) complete forgetfulness of the Natural Law by mankind is impossible.
320. Those who have not the use of reason, either habitually (as children and the insane) or actually (as the intoxicated), may be invincibly ignorant of the Natural Law—for example, they may be unable to perceive even the difference between right and wrong. As to those who have the use of reason, they can be ignorant of the Natural Law only as follows:
(a) they cannot ever be invincibly ignorant of the most general precepts (such as "good is to be done," "evil is to be avoided"), for since they know the difference between right and wrong, they must also perceive that which is contained in the concepts of right and wrong, viz., that the former is something desirable and which ought to be done, the latter something undesirable which must not be done;
(b) one cannot, as a rule, be invincibly ignorant of those precepts that are immediately inferred as necessary conclusions from the most general precepts (such as "that which was borrowed must be returned"), for the conclusion follows so easily from the manifest principle that only in exceptional cases could one be excused for not knowing its truth;
(c) one can, even as a rule, be ignorant of precepts that are inferred as necessary but very remote conclusions from the most general precepts, (such as "that which was borrowed must be returned at such a time or place, or in such a manner or condition"), for this conclusion is so far removed from its premise, and there are so many factors to be considered, that considerable knowledge and skill in reasoning are required for a correct judgment—things in which many people are lacking.
321. The Commandments of the Decalogue follow directly from the most general precepts of the Natural Law, and so to them may be applied what was said in the previous paragraph. Hence: (a) generally speaking, no person who has the use of reason can be invincibly ignorant of the Commandments. St. Paul blames the pagans as inexcusable in various sins committed against the Decalogue; (b) in special cases, a person who has the use of reason can be invincibly ignorant of one or more Commandments; for while the Commandments may be easily inferred by most persons from the common principles of right and wrong, there are sometimes involuntary impediments that hinder the right employment of reason. Thus, children and older persons whose mentality is undeveloped, although they know the difference between right and wrong, are frequently unable to draw the conclusion that follows from it (e.g., that one should not tell lies).
322. The Commandments regarding which invincible ignorance may most easily exist are: (a) those that deal with merely internal acts, for the malice of violating them is less apparent. Hence, many theologians admit that even among Christians the wickedness of sinful thoughts and desires may be inculpably unknown, at least when the wickedness of the corresponding external acts is also not known; (b) those that deal with the control of sensuality, for the impulse to inordinate acts is at times most vehement. Unde theologi sunt qui affirmant malitiam peccatorum externorum contra sextum invincibiliter ignorari posse, non solum apud infideles, sed etiam apud Christianos, ita quod ab adolescentibus facile ad tempus ignorari possit malitia mollitiei.
323. If a Commandment be applied to some particular case in which there are many circumstances to be considered, or some reason that appears to change the subject-matter of the law, even adults who have the perfect use of reason may be invincibly ignorant; for in such instances we are considering, not an immediate, but a remote conclusion from the general principles of Natural Law.
(a) If the case is difficult relatively (i.e., in view of the training or lack of education of the person studying it), there can be invincible ignorance, at least for a time. Examples: Jepthe, according to St. Jerome, appears to have been invincibly ignorant that it was not lawful for him to slay his daughter. Being a soldier and living in a rude age, he perhaps did not appreciate the sacredness of human life. Unlettered persons might conceivably think in good faith that it is not wrong to commit perjury in order to help one in danger, to steal in order to pay debts, to think evil if there is no intention to fulfill it, to do what the majority do or what is tolerated, etc.
(b) If the case is difficult absolutely (i.e., in view of the matter itself, which is complicated and obscure), there can be invincible ignorance, even for a long time. Thus, it is so difficult to settle many problems pertaining to justice (i.e., to the application of the Seventh Commandment) that we find professional theologians who take opposite sides, or admit that, speculatively speaking, they do not know where the truth lies.
324. The Natural Law can never be erased from the hearts of men. (a) In abnormal circumstances only, as when the general power of reasoning has been weakened or lost, can the Natural Law be forgotten. Thus, to a degenerate who becomes violently insane murder and other crimes may appear as good acts. But no community could govern itself by the standards of madmen and long survive. (b) In normal circumstances (i.e., as long as the general power of reasoning remains unimpaired), the Natural Law cannot be forgotten, as far as its general principles or immediate conclusions are concerned, although it may be overlooked or lost sight of when it is applied to particular cases, or when remote conclusions are deduced from it.
325. As long, therefore, as a body of men remain sane, even though they be uncivilized or addicted to crime, they cannot become oblivious of the Natural