"Then he called the crowd again and said to them, ‘Listen to me, all of you, and understand: there is nothing outside a person that by going in can defile, but the things that come out are what defile.’ For it is from within, from the human heart, that evil intentions come: fornication, theft, murder, adultery, avarice, wickedness, deceit, licentiousness, envy, slander, pride, folly. All these evil things come from within, and they defile a person.’"I am sure the list is incomplete even though Mark includes six more evils than Matthew (15:19), but I had to stop and wonder about "folly" and how it got in there.
To modern ears, folly or foolishness might be considered an act of ignorance, stupidity, or perhaps the result of an innocent mistake, but according to the Jamieson-Fausset-Brown Bible Commentary
foolishness "—in the Old Testament sense of 'folly' is criminal senselessness, the folly of the heart."
I am not quite sure about what exactly Mark was referring to when he wrote "folly," but perhaps the modern definition of a senseless crime as "a crime for which there seems to be no identifiable motive such as lust, revenge, or greed" (Psychology Today) might approximate what he was getting at.
Mark's list: fornication, theft, murder, adultery, avarice, wickedness, deceit, licentiousness, envy, slander, pride, folly make up what the Commentary rightly describes as an "appalling black catalogue." Such is the stuff that lies within the human heart. None of us are immune to the temptation of perusing that catalogue from time to time.
These evils from the heart are but a few of the many things that dog us all and demonstrate to me that the forgiveness we are offered by God is far greater than anything we can imagine.
And for that we should be eternally grateful.