Lapin, president of Toward Tradition, a national coalition of Jews and Christians, compares Walker to Chandra Levy, who disappeared amid questions about her relationship with Rep. Gary Condit.
Writes Lapin, "They came from homes in which they received from their parents the same unfortunate message. Chandra's father is sort of Jewish while her mother is sort of a Buddhist.
"Johnny's mother is also sort of a Buddhist while his father is sort of Catholic."
According to Lapin, this is the message John Walker's and Chandra Levy's parents sent them: "Yes, your father and I agree on all the important things in life, like where to vacation and how to decorate the house.
"But on less important matters -- having to do with beliefs and values, for instance religion -- we don't mind disagreeing."
Almost 2,000 years ago, another rabbi, the apostle Paul, instructed parents to bring their children up "in the discipline and instruction of the Lord" (Ephesians 6:4). Elaborating on this verse, Luther uttered a sentence that must sound familiar to boomer ears: "Don't teach them your own thing."
Neither Paul, nor Luther nor Lapin intended an offense to religions other than theirs. Their point is: Young people need clarity in religious matters, not mush.
If they are normal, they are seekers by nature. Walker certainly was. In a Newsweek interview, his father called him "a spiritual kid." But this was a meaningless post-modern expression.
You can be "spiritual" if you worship the devil or your ancestors or indeed yourself. "Spirituality" says nothing about absolute values. Thus it should not surprise us that a mere 13 percent of the baby buster generation (18-36 years old) told pollsters of the Barna Research Group they believed in absolute moral truth.
This is the disastrous culmination of a post-Enlightenment development George Weigel, a senior fellow at the Washington-based Ethics and Public Policy Center, chastises as a pursuit not of the right to freedom but to willfulness.
In the present case, this means the willfulness not of John Walker or Chandra Levy but of their parents' generation proclaimed as salutary the catastrophic dictum: Do your own thing.
"A son like Johnny or a daughter like Chandra never saw modeled for them, by a parent, what it means to have strong convictions about ultimate questions," says Rabbi Lapin.
"They never knew the difference between sham convictions and authentic ones. Thus children grow up dangerously vulnerable to strong personalities (Gary Condit) or strong religions (Islam), gurus or other substitutes for what they never got at home."
"Parents should be apostles to their parents," Luther insisted. He meant of course Christian apostles. But a Jew or a Buddhist or a Hindu grounded solidly in their faiths would give similar answers to the foolish cliche that oozed out of the 1960's: "We don't raise our children in any religion -- let them decide for themselves when they have grown up."
The truth is that they won't be able to do so. Uninstructed, they will have been rendered defenseless, just like "Johnny and Chandra," to paraphrase Lapin.
As an orthodox rabbi, Lapin sees the solution in the Torah, which places a tremendous stress on making sure that husband and wife profess the same religion. "Now you know why the Torah insists," he writes in his commentary on the Walker case.
Luther would not have gone that far. "As I am allowed to eat, drink, sleep, go out, speak and do business with a heathen, Jew, Turk or heretic, so I may also marry and remain in that state," he said.
But his underlying assumption was that at least one partner in such a marriage -- to Luther it was clear that this should be the Christian -- would catechize his offspring.
Post-modernity's failure to do this has produced this era's worst dilemma: a generation of religious illiterates with shifting values and a yearning they cannot properly still because their parents have left the larder empty.
John Walker Lindh is one among millions, except that he took a more extreme route than most.