Adam, a young businessman not quite 30, raised as an evangelical Christian, thoughtful, well-read, and free-spirited, contacted me recently at the suggestion of a mutual friend. He was concerned about his grandmother, Carolyn, nearing 80, a lifelong Christian Scientist married to an agnostic, and now facing grave health concerns. (I’ve changed their names for privacy.)

I took Adam to lunch and we talked for a long time. Knowing I had come to the Cross from Christian Science at about age 40, he wanted help making sense of Carolyn’s dogged resistance to both the skeptical arguments of her husband and the biblical appeals of himself as a grandson. (Also the appeals of a son, since Adam’s father is an evangelical too.)

What is it about Mrs. Eddy’s system, Adam asked, that can take such an unshakable hold on someone like his grandmother? His eyes got big when I showed and explained to him “Science and Health with Key to the Scriptures,” which he had never seen before. We talked about the power of the system’s claim to be scientific, and the high ground seized by its pretension of being the Bible’s only reliable interpreter. The latter is clinched by the Glossary chapter, I pointed out, and the former by the Fruitage chapter.

Adam said that his psychology-professor grandfather, Herb, endlessly objects that a real science would study and acknowledge its failures as well as its successes, but Carolyn brushes that off. I concurred that no accounts of healing unachieved appear in the Fruitage chapter, nor are such matters taken up in the Scientists’ testimony meetings or the periodicals.

The copy of Mrs. Eddy’s textbook that I had brought to lunch happened to be one where I have marked every Bible quotation or allusion in the entire book, hundreds of them in all. Adam began to see how the massive combined weight of scriptural references and distortions — buttressed with the groupthink of “it must be true, it heals” — weaves a web of plausibility and comfortable Gnostic belonging around good people like Carolyn.

But what about her reliance on dentistry and eyeglasses, he wanted to know: how does that square with the professed standard of health care by spiritual means alone? Of course it doesn’t. Yet by such suspensions of logic and common sense, grown numbingly familiar during more than a century (six generations in some families), has the system eased its rigidity just enough to permit continuance of the self-reinforcing mentality of acceptance that carries a believer along.

Nonetheless, Adam told me, a recent severe illness had so frightened Carolyn that she yielded to Herb’s pleading for a medical diagnosis, underwent hospitalization, and — at the time of our conversation — was cooperating with a course of blood treatments prescribed as vital to her survival.

The young man praised God for this much deviation on his grandmother’s part. But as we ended the lunch, he said his continuing prayer is for her to renounce Christian Science not just medically but theologically, and come to a saving knowledge of Jesus Christ before she dies. In which prayer I join.