Heroin addiction is poignantly tragic. Users build tolerance, so larger hits are required for the same high. Soon the dosage they seek is more than enough to kill them. When addicts hear someone has died from an exceptionally strong batch, their first thought may not be fear but “Where can I get that?”

C. S. Lewis warned of this downward spiral in Screwtape Letters, his imaginative look at a demon’s explanation of the art of temptation. Start with some pleasure—if possible one of God’s good pleasures—and offer it in a way God has forbidden. Once the person bites, give less of it…