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 Law. (a) The general principles (“good is to be done,” “evil is to be avoided”) cannot vanish from the mind, although, in particular affairs, anger, pleasure, or some other passion may prevent men from thinking about them. Thus, when the mob spirit takes hold of a crowd, it becomes intent only on violence or revenge, and gives no thought to conscience. (b) The secondary precepts, such as those contained in the Decalogue, cannot be obliterated from the mind, although in applying them to concrete situations a people may go astray.