185. Imperfections.—The description of venial sin just given indicates that it is a voluntary transgression of the law of God in matters of lighter importance, and is thus distinguished from the various classes of moral imperfections. These latter imperfections are:
(a) natural imperfections, which are the falling short on the part of good acts of the higher degree of goodness they might have possessed. Since man is finite by nature, it is inevitable that he be limited in the good he does; and hence this kind of imperfection is not a transgression or a sin;
(b) personal imperfections which are voluntary but not transgressions, are acts or omissions whose motive is reasonable, but which are contrary to that which is of counsel. Example: to omit hearing a Mass that is not obligatory, when one is able to assist at it, but has a good reason for staying away;
(c) personal imperfections which are transgressions but not voluntary, are acts or omissions done without deliberation, but which are opposed to some law of less importance. Example: To pray with involuntary distractions.
186. Change in the Gravity of Moral Defects.-An imperfection becomes a sin: (a) if the motive for omitting what is of counsel only is sinful (e.g., to neglect a Mass that is not of obligation out of contempt); (b) if a slight indeliberate transgression has a cause that was voluntary (e.g., involuntary distractions caused by previous neglect).
187. Venial sins become mortal when that which in itself is a slight offense, becomes in the individual agent a grave offense by reason of some change in the object or of some grave malice in the purpose, circumstances, or the foreseen results (see above 97 sqq.).
188. A change in the object makes venial sin mortal: (a) when that which is light matter objectively is apprehended subjectively as grave matter (e.g., a person tells a small lie or commits a trifling theft, thinking these to be mortal sins); (b) when that which is light matter by itself becomes knowingly grave matter through the additions that are made to it (e.g., a thief steals small amounts frequently with the intention of having a great amount of ill-gotten money after a time).
189. It should be noted that, while the matter of venial sins may coalesce so as to form grave matter and constitute a mortal sin, as just explained, venial sins themselves do not, from mere multiplication, ever become mortal, since the difference between mortal and venial sin is not one of quantity, but of kind. Hence, when acts are slightly sinful but do not coalesce, they multiply venial sins, but do not form mortal sin. Example: Coming a few minutes late for Mass every Sunday.
190. The multiplication of venial sins, especially when they are held as of no importance, disposes for the commission of mortal sin: (a) directly, by forming a habit that calls for ever greater indulgence (e.g., petty thefts lead to dishonesty on a large scale); (b) indirectly, by familiarizing one with wrongdoing and chilling the love for virtue.
191. The wrong purpose of the agent makes an act that is only venially sinful (as far as the object is concerned) to become mortally sinful, when the purpose contains a grave malice in itself, for the act is then intended only as a means to what is seriously wrong (see above 80). Example: To tell a small lie in order to break up friendships and sow hatreds.