Day 248: The Spread of Sin

Sin creates a proclivity to sin; it engenders vice by repetition of the same acts. This results in perverse inclinations which cloud conscience and corrupt the concrete judgment of good and evil. Thus, sin tends to reproduce itself and reinforce itself, but it cannot destroy the moral sense at its root. CCC 1865

Today's reading is five short paragraphs on the proliferation of sin, followed by an In Brief reviewing what has been covered over the past few days. These vices engendered by "repetition of the same acts" are like a gateway drug that can lead one to what traditionally are classified as the Seven Deadly Sins. The Catechism Compendium summarizes these:

Vices are the opposite of virtues. They are perverse habits which darken the conscience and incline one to evil. The vices can be linked to the seven so-called capital sins, which are: pride, avarice, envy, anger, lust, gluttony, and sloth or acedia. (#398)

We are responsible for our own bad choices, not those of others, except when we participate or cooperate in their sins. 

The Catechism Companion, Vol III has some good commentary on this:

Sin can spread like a virus. As love begets love and virtue begets virtue, sin begets sin. When we choose sin, it becomes easier to choose sin... We must stand up to protect others who are being hurt by someone's sins, even if it costs us something. Fighting against these sins is hard, yet we must protect the vulnerable among us. God poured out his life for us and gives us the grace and strength to be the people we can be for the people around us. (p. 12)