Article — Wouters, Manual of Moral Theology
Article III. On Certain Other Works of Spiritual Mercy
Somewhat akin to fraternal correction are: 1. instruction of one who through ignorance is about to transgress a grave law; 2. admonition of one who is in danger of sinning formally.
I. The instruction of which we speak obliges:
Of itself, if there is question of divine law, whether natural or positive: namely on account of the reverence due to a law of this kind. If there is question of human law, it quite probably does not oblige, because it is not sufficiently certain that the reverence due to such a law demands this (St. Alphonsus, II, 36).
As it were by accident, instruction, even if there is question of human law, can oblige: 1. on account of the harm of the one ignorant, as if he is ignorant of things to be known by necessity of means; if there is danger lest he contract a bad custom; if he is ignorant of a prohibition of civil law, and therefore is about to expose himself to the danger of a penalty; 2. on account of common harm or the harm of a third party, as if someone through ignorance were detaining another's property; 3. on account of scandal, as if an unknowing priest were to enter a brothel.
Superiors, confessors, parish priests, parents, and teachers are of themselves always bound to instruction, "because upon them it specially falls to teach subjects" (St. Alphonsus, II, 36).
Note, however, that a proportionate cause excuses from the obligations set out.
II. Admonition, as is clear, must of itself be made if one's neighbor is in grave danger of sinning formally; moreover apply to this matter what has been said about correction.
III. Finally, concerning the spiritual works of mercy, it helps to note these things:
Since the Church herself, especially through religious Orders and Congregations, endeavors to provide for the propagation of the faith, no one in particular is bound to go to the regions of unbelievers, unless legitimate authority imposes this upon him. Moreover, all should contribute to the intended end by alms or at least by prayers (St. Alphonsus, II, 27).
It is difficult to determine accurately how far the dead must be helped; but it is certain that the faithful who fulfill their Christian duties satisfy the obligation: for so often they are present at the Sacrifice of the Mass and at public prayers, which are made for the dead or even for them.1
1 Aertnys-Damen, I, n. 372, question 30.