How Do I Talk About Degrees of Sin?
Many non-Catholics say, "A sin is a sin. There is no sin greater than another.” How would you respond using Scripture?
Perhaps the best passage to show your Protestant friend is 1 John 5:16-17:
If any one sees his brother committing what is not a mortal sin, he will ask, and God will give him life for those whose sin is not mortal. There is sin which is mortal; I do not say that one is to pray for that. All wrongdoing is sin, but there is sin which is not mortal.
Some translations translate “mortal” as “unto death” and “not moral” as “not unto death.” The death that John speaks of here is not physical death but spiritual death. Therefore, different sins can have different spiritual effects. Some sins cause spiritual death, and others do not. This is the basic understanding of the Catholic teaching on mortal and venial sin.
Other passages that hint to sin having different degrees of gravity are Luke 12:47-48, Matthew 5:19, 5:21-22; James 1:15, 3:1; and John 19:11.