If the problem with socialism is, as Mrs. Thatcher says, that eventually you run out of other people’s money, much of the West has advanced to the next stage: It’s run out of other people, period. Greece is a land of ever fewer customers and fewer workers but ever more retirees and more government. How do you grow your economy in an ever-shrinking market? The developed world, like Elisabeth, is barren. Collectively barren, I hasten to add. Individually, it’s made up of millions of fertile women, who voluntarily opt for no children at all or one designer kid at 39. In Italy, the home of the Church, the birthrate’s somewhere around 1.2, 1.3 children per couple — or about half “replacement rate.” Japan, Germany, and Russia are already in net population decline. Fifty percent of Japanese women born in the Seventies are childless. Between 1990 and 2000, the percentage of Spanish women childless at the age of 30 almost doubled, from just over 30 percent to just shy of 60 percent. In Sweden, Finland, Austria, Switzerland, the Netherlands, and the United Kingdom, 20 percent of 40-year-old women are childless. In a recent poll, invited to state the “ideal” number of children, 16.6 percent of Germans answered “None.” We are living in Zacharias and Elisabeth’s world — by choice.

America is not in as perilous a situation as Europe — yet. But its rendezvous with fiscal apocalypse also has demographic roots: The Baby Boomers did not have enough children to maintain the solvency of mid-20th-century welfare systems premised on mid-20th-century birthrates. The “Me Decade” turned into a Me Quarter-Century, and beyond. The “me”s are all getting a bit long in the tooth, but they never figured there might come a time when they’d need a few more “them”s still paying into the treasury.

The notion of life as a self-growth experience is more radical than it sounds. For most of human history, functioning societies have honored the long run: It’s why millions of people have children, build houses, plant trees, start businesses, make wills, put up beautiful churches in ordinary villages, fight and if necessary die for your country . . . A nation, a society, a community is a compact between past, present, and future, in which the citizens, in Tom Wolfe’s words at the dawn of the “Me Decade,” “conceive of themselves, however unconsciously, as part of a great biological stream.”