Thomas Aquinas

“ Further, the avoidance of any sin is a spiritual good, since any sin brings spiritual harm to the sinner. Now it seems that one ought sometimes to commit a venial sin in order to avoid scandalizing one's neighbor, for instance, when by sinning venially, one would prevent someone else from committing a mortal sin: because one is bound to hinder the damnation of one's neighbor as much as one can without prejudice to one's own salvation, which is not precluded by a venial sin. Therefore one ought to forego a spiritual good in order to avoid scandal. ”

“ Passive scandal cannot be a special sin, because through another's word or deed a man may fall into any kind of sin: and the fact that a man takes occasion to sin from another's word or deed, does not constitute a special kind of sin, because it does not imply a special deformity in opposition to a special virtue. ”

“ Sometimes therefore it happens that there is active scandal in the one together with passive scandal in the other, as when one commits a sin being induced thereto by another; sometimes there is active without passive scandal, for instance when one, by word or deed, provokes another to sin, and the latter does not consent; and sometimes there is passive without active scandal, as we have already said. ”

“ On the other hand, as regards those temporalities of which we have the dominion, sometimes, on account of scandal, we are bound to forego them, and sometimes we are not so bound, whether we forego them by giving them up, if we have them in our possession, or by omitting to claim them, if they are in the possession of others. ”

“ Further, since among virtuous or right acts one is more virtuous or more right than another, that one alone which has perfect rectitude would not seem to be a "less" right one. If, therefore, scandal is something "less" rightly said or done, it follows that every virtuous act except the best of all, is a scandal. ”

“ Or scandals must needs occur, seeing the condition of man who fails to shield himself from sin. Thus a physician on seeing a man partaking of unsuitable food might say that such a man must needs injure his health, which is to be understood on the condition that he does not change his diet. In like manner it must needs be that scandals come, so long as men fail to change their evil mode of living. ”

“ For, as Jerome says on this passage, "it is much better to receive a brief punishment for a fault, than to await everlasting torments." Therefore scandal is a mortal sin.
Objection 3: Further, every sin committed against God is a mortal sin, because mortal sin alone turns man away from God. Now scandal is a sin against God, for the Apostle says (1 Cor. 8:12) : "When you wound the weak conscience of the brethren [*Vulg.: 'When you sin thus against the brethren and wound their weak conscience'] , you sin against Christ." Therefore scandal is always a mortal sin. ”

“ Sometimes we ought to suffer those who rob us of our temporalities, while sometimes we should resist them, as far as equity allows, in the hope not only that we may safeguard our property, but also lest those who take what is not theirs may lose themselves. ”