Article V: On the Conversion of Mortal and Venial Sin

St. Thomas, I-II, q. 88, a. 4, 5, 6; De Malo q. 2, a. 8; q. 7, a. 3 and 4.

547. The conversion of mortal sin into venial, and vice versa, is not to be understood as if the same act in number of mortal sin which now exists in the concrete with all its circumstances could become venial; but that an act of sin which from the genus, by reason of itself, in the abstract is mortal, can be only venially evil according as in the concrete here and now it exists with its circumstances; and vice versa.

548. Mortal sin per se or from the genus can become venial, not indeed per accidens from a venially evil circumstance added to the act, because a light deformity added rather increases sin than diminishes it; but:

a) If it is mortal from the whole genus, it becomes venial only from a disposition of the agent which subtracts something from the act: 1. from an erroneous conscience which without grave negligence judges to be venial what is mortal; 2. from imperfect deliberation; and 3. from imperfect consent.

b) If it is mortal from its own genus, it becomes venial from the three aforesaid modes, and besides 4. from lightness of matter or on the part of the object, for example, theft.

Venial sins from imperfect deliberation or imperfect consent are called venial from imperfection of the act: for they are imperfect human acts. According to St. Thomas, imperfect deliberation and imperfect consent are possible in every matter.

549. Venial sin according to itself becomes mortal, whether a) on the part of the agent on account of a circumstance or disposition mortally evil, - or b) on the part of the act on account of a circumstance which changes the species and adds grave malice distinct in species; - or c) from coalescence, multiplication, or aggravation of matter. And indeed:

1. from an erroneous conscience which judges or doubts that what is only venial is mortal;

2. by reason of the ultimate end, when the sinner constitutes his ultimate end in venial sin, that is, when he is prepared to sin mortally on account of that sin which of itself is venial, for example, to omit Mass in order to play excessively or to steal a small thing;

3. by reason of an adjoined end, as if someone says a light lie or a lightly dishonest word in order to fornicate, or commits a light theft for homicide;

4. from formal and perfect contempt of the precept or the one commanding, by which man violates the precept precisely because it is a precept, whatever it may be, whether grave or light, - or because the superior insofar as he is superior commands, whatever he commands;¹

¹ Not, however, because the superior commands only something light or something inept, or because he himself is imprudent or wicked.

5. by reason of grave scandal, as if you foresee that through a dishonest word you are an occasion to another of sinning gravely;

6. by reason of proximate danger of falling into mortal sin, to which the sinner would expose himself without sufficient caution or necessity, for example, conversation with a woman for a fragile man: furthermore, to danger of which mortal sin he exposes himself must be declared in confession;

7. by reason of notable harm which is foreseen to follow from the sin for neighbor, for example, if a light theft would place another in extreme necessity, or a quarrel would arise from excessive loquacity;

8. by reason of coalescing or multiplied matter, as must be explained specially.

The first seven modes are also valid for venial sin from its own genus; the last only concerning venial sin from lightness of matter.

550. The rule for discerning whether venial sin from lightness of matter becomes mortal from aggravation and multiplication of matter is the following: Several small matters can coalesce and are morally united into one grave matter when they pertain to the same precept in number and to one transgression of the precept.

Thus small thefts coalesce into one gravely unjust detention or damaging; likewise several small eatings, or omissions in the hours, had on the same day into one violation of the fast, or grave omission of the breviary; - on the contrary, several small eatings or omissions had on different days do not coalesce because they do not pertain to the same precept in number, nor do several light excesses in drink had on the same day coalesce: for since they do not consist in a permanent thing, they do not pertain to one and the same transgression; nevertheless they can coalesce into one harm to health or to the family, because in the account of harm they are something permanent.

He who by several light transgressions arrives at grave matter, if he intended this from the beginning, commits one mortal sin; but if he did not intend this, he commits as many venial sins as there were light transgressions, except the last, which is mortal, because through it grave matter is completed: for by this act he wills the small matter insofar as it is united with the others for composing grave matter.

Light transgressions following upon grave matter already completed, if they were intended from the beginning, constitute one mortal sin with the prior ones but aggravate it externally; - but if they were not intended, they do not constitute a new mortal sin unless they again attain a new grave quantity: but if nevertheless they were considered as one thing with the preceding grave matter, they include the mortal sin of joy or approval concerning it.