Question C: How do venial sins lead to mortal sins?

1. The lives of Christians manifest both the imperfection of immaturity and the imperfection of disintegrity. Many desires and objectives are pursued without reference to living faith. This generates temptations and inevitably leads to venial sins. Some are recognized as sins; others are done with some awareness of their unreasonableness but no clear grasp of their sinful character; and still others are done more or less without moral reflection.

2. Venial sins can lead to mortal sins in four ways. All are similar in that they involve the venial sin’s effect of opening up mortally sinful options or providing grounds for choosing them. Yet they are distinguishable.

Christian writers always have recognized that venial sins are serious, especially because they somehow lead to mortal sin. However, from the time of St. Augustine, who suggested the metaphor that many drops make a river and many grains a lump (see FEF 1846), the explanation of the relationship between venial and mortal sins usually has lacked the clarity one might wish. St. Thomas Aquinas is more helpful in indicating how sins can be causally related (see S.t., 1–2, q. 75, a. 4; q. 84, a. 1; q. 88, a. 3). Although he is not concerned exclusively with the relationship of venial to mortal sins, his ideas can be adapted to explain this matter.

3. First, venial sins can supply new options, fresh occasions, for sinning mortally. By lying and disobedience, for example, children and young people gain liberty to go places and do things which offer occasions of mortal sin. Similarly, venial sins committed in acquiring wealth confer the power to be self-indulgent, while venial sins of defect in diligence in forming conscience free one to consider gravely wrong possibilities without at first attending to their full danger.

4. Second, venial sins involve committing oneself to certain goods in whose enjoyment one grasps further sinful possibilities which might otherwise have remained unknown. For instance, children’s sins of impurity, which can be venial because of lack of sufficient reflection, make similar acts live options even after their gravity is known. Venially sinful acts of stealing can foster a taste for easy possession. One accustomed to deliberate lying takes a stance toward relevant goods which paves the way for mortal sins of lying.

5. Third, venial sins often create situations which it is difficult to escape without mortal sin. For example, venial sins committed in seeking popularity give rise to companionships with people who do not respect Christian faith and so lead to temptations to compromise faith in order to avoid embarrassment. A venial sin of carelessness can lead to an accident, which easily generates a temptation to sin mortally by evading grave duties—for example, by leaving someone injured at the scene. Venial sins of waste place people in a position of need, so that they are tempted to grave sins of theft.

6. Fourth, venial sins often generate objectives one is tempted to pursue through mortal sins. Venial sins of self-indulgence may accustom one to a standard of living which one is tempted to maintain by such means as theft, prostitution, or immoral methods of family limitation. Venial sins of status seeking may place one in a position where one is tempted to do whatever is necessary to acquire the status one craves—deny one’s faith, cheat, offer illicit sexual favors or bribes, lie under oath, and so on.

This consideration of the seriousness of venial sin and its dynamic relationship to imperfection (from which it arises) and to mortal sin (to which it tends) makes clear the wisdom of using all available means to combat venial sin from the very beginning of moral life. One of these means is an early and regular use of the sacrament of penance (see 32‑D).