Start with the car seats. They hulk in the back seats of any normal sedan, squeezing the middle seat from both directions, built like a captain’s chair on Star Trek if James T. Kirk was really worried about taking neck damage from a Romulan barrage. The scenes of large-family life from early in the automobile era, with three or four kids jammed happily into the back seat of a jalopy, are now both unimaginable and illegal. Just about every edition of Cheaper by the Dozen, published in 1948, uses an image of the Gilbreth kids packed into the family automobile, overflowing like flowers from a vase. Today, the car seats required to hold them would take up more space than the car itself.

In his 2013 book, What to Expect When No One's Expecting, Jonathan V. Last described “car seat economics” – the expense and burden of car seats for ever-older kids, the penalties imposed on parents who flout the requirements – as an example of the countless “tiny evolutions” that make large families rarer. Obviously car seats aren’t as big a deal as the cost of college or childcare, or the cultural expectations around high-intensive parenting. But it’s still a miniature case study, Last suggested, in how our society’s rules and regulations conspire against an extra kid.

Our society’s future would be radically different if people simply had as many kids as they desired.

Seven years later, two economists set out to prove him right. In a paper entitled “Car Seats as Contraception,” they argued that car-seat requirements delay and deter the arrival of third children, especially, because normal backseats won’t hold three car seats, so you basically can’t have a third young kid in America unless you upgrade to a minivan. The requirements save lives – fifty-seven child fatalities were prevented in 2017, the authors estimate. But they prevent far more children from coming into existence in the first place: there were eight thousand fewer births because of car-seat requirements in 2017, according to their calculations, and 145,000 fewer births since 1980.

You don’t have to quite believe the specificity of these numbers to see that an important truth is being revealed. Our society is not exactly more hostile to children than societies in the past: indeed, once an American child is born, her girlhood will be safer from all manner of perils than the childhoods of the 1980s, let alone the farm-and-factory past. But this protectiveness coexists with a tacit hostility toward merely potential children – children who might exist, children who are imagined when people are asked about their ideal family size, but who, for all kinds of reasons, are never conceived or never born.

We lack a moral framework for talking about this problem. It would make an immense difference to the American future if more Americans were to simply have the 2.5 kids they say they want, rather than the 1.7 births we’re averaging. But talking about a declining birthrate, its consequences for social programs or economic growth or social harmony, tends to seem antiseptic, a numbers game. It skims over the deeper questions: What moral claim does a potential child have on our society? What does it mean to fail someone who doesn’t yet exist?

I think about this with our daughter Rosemary, our fourth child, six months old as I write. We weren’t sure if we could have her, or if we should. I had been sick with a debilitating illness that maybe – not officially, but definitely anecdotally – can be passed along to children. My wife carried the scars of several caesarean sections. We had moved three times in five years, losing money as we went. Much more than with any of her siblings, having Rosemary was a leap of faith.

She was conceived in the summer of 2019. In the winter of 2020, I brought Covid-19 home to my family from a book tour, and our other children and my seven-months-pregnant wife got sick. Rosemary was born amid the first wave of the pandemic; her birthday matches the exact late-April peak of deaths for our home state of Connecticut.

After we brought her back from the hospital, healthy and cheerful, I thought about what would have happened if news from 2020 had fallen back through a wormhole into 2019. Guess what? Before you conceive another child, you should know that there will be a pandemic next year, the economy will shut down, there will be riots and a crime wave, and you’ll all get sick with the virus, deep into your wife’s pregnancy. Would Rosemary have been conceived in the shadow of that foreknowledge? Would we have made the leap?

Because of course now that she is here she has inestimable value. How could the challenges of 2020, however dire they might have sounded as prophecy, possibly justify her non-existence? How could we not have pressed ahead, if the endpoint was her friendly cheeks, her babyish giggles, her oh-so-human eyes?

The idea that not-enough-Rosemarys might be a problem for the world has taken a long time to take hold. The consensus during my youth held that falling birthrates were always a sign of progress, that Third World overpopulation might doom the world to famine, and that anyone who cared too much about Western fertility was probably a crank.

I took this gospel for granted as a child: I remember quizzing my dad about how the earth could possibly survive the combination of overpopulation and pollution. But I also came young to the realization that the problem might lie elsewhere. Sometime in Bill Clinton’s presidency, I was assigned a high school science bulletin-board project on population trends. In the library I checked out all the books on overpopulation – which meant basically the collected works of Paul Ehrlich, the alarmist author of The Population Bomb. When I compared their 1970s-era projections to what was actually happening, my teenage self could see two things plainly: first, none of the disasters Ehrlich envisioned had come to pass, and second, for the rich world the population trend was an arrow pointing down and down and down.

The birthrate is entangled with any social or economic challenge that you care to name.

I was hardly the first person to notice this: P. D. James’s dystopian prophecy of mass infertility, The Children of Men, came out five years before my bulletin-board revelation. But the fear of under population belonged to the realm of weirdos and conservatives (but I repeat myself) well into my adulthood. When Hollywood got around to adapting James’s novel in 2006, the film focused more on terrorist disturbances and cruelty to immigrants than the horror of a childless world. When countries in East Asia and then Eastern Europe began to search for policies to bolster birthrates, they were regarded as illiberal curiosities.

It was only when the US birthrate, long an above-average outlier among rich nations, began to descend anew following the Great Recession that the topic began to spark stirrings of real interest. But even now there’s no agreement that the birthrate deserves as much attention as healthcare or taxes or abortion or police brutality, let alone that it might be one of the most pressing issues of our time.

Yes, Republicans can be induced to include a little family-friendly tax policy in a larger tax reform, and Democrats support family subsidies when they’re cast as measures to fight poverty. But to argue that the American future depends on pushing our birthrate back above replacement level, as Matthew Yglesias did in his recent book One Billion Americans, remains an eccentric argument to many people: an interesting idea, maybe, but not a particularly urgent one, and certainly not the sort of issue that would make the cut of questions for a presidential debate.

Which is a bit crazy, when you stop to think about it. Whether a society is reproducing itself isn’t an eccentric question; it’s a fundamental one. The birthrate isn’t just an indicator of some nebulous national greatness; it’s entangled with any social or economic challenge that you care to name.

As social scientists have lately begun “discovering,” a low-birthrate society will enjoy lower economic growth; it will become less entrepreneurial, more resistant to innovation, with sclerosis in public and private institutions. It will even become more unequal, as great fortunes are divided between ­ever smaller sets of heirs.

These are just the immediately measurable effects of a dwindling population. They don’t include the other likely effects: the attenuation of social ties in a world with ever fewer siblings, uncles, cousins; the brittleness of a society where intergenerational bonds can be severed by a single feud or death; the unhappiness of young people in a society slouching toward gerontocracy; the growing isolation of the old.

Families can be over-sentimentalized, imprisoning, exhausting. But they supply goods that few alternative arrangements can hope to match. No public program could have replaced the network of relatives that helped my grandfather live independently until his death – even if, yes, his five children, my mother and aunts and uncles, had often feuded with him and each other over the years. No classroom is likely to supply the ­education in living intimately with other human beings that my children gain from growing up together – even if the virtue of forbearance is not always perfectly manifest in their interactions.

Yea, thou shalt see thy children’s children, and peace upon Israel, runs the Psalmist’s blessing. A society of plunging birthrates withdraws the first blessing, and compromises the second day by day.

But to identify these problems is to run into a question: Whose responsibility, exactly, is it to fix them? One reason that the healthcare system and the tax code come up at presidential debates is that both involve official choices about how to regulate and spend. But the government cannot conjure babies (yet), and fertility decisions belong to an intimate sphere that we rightly insulate from the reach of state coercion. And modern societies feel uncertain about whether they can even ask people to have kids, since that implies a moral obligation to have children.

Such an obligation was assumed by most peoples in human history, but most peoples were not us: freed from patriarchal demands, liberated from economic systems in which an extra pair of hands is an automatic asset, proud of the opportunities available to women, too secular to accept “be fruitful and multiply” admonitions, and conscious that there are eight billions of us and counting on an earth whose environment is, put mildly, under strain.

Still, even for a secular society it isn’t hard to generate a moral-obligation-to-procreate case. You can just play the utilitarian game: Society should seek the greatest good for the greatest number; there is no good so essential as existence, so society should be organized to maximize, within reason, the number of people that exist.

I said within reason because that’s how even the most child-friendly parents tend to think. You have to go pretty deep into religious traditionalism to find people who don’t do anything to space their children, and put their childbearing exclusively in the hands of God. The rest of us, even the people who embody what a Washington Post journalist once called “smug fecundity,” tend to balance the number of kids they have against some other perceived good: not just health or the demands of some humanitarian vocation, but education, real estate, professional ambition. And, of course, the desire to someday get a little sleep.

But maybe this “reasonability” concession gives too much away. A famous rejoinder to the utilitarian case for more kids is that it leads to what the philosopher Derek Parfit termed the “Repugnant Conclusion” – namely, that so long as we consider existence itself a utilitarian trump card, we have to conclude that for “any possible population of at least ten billion people, all with a very high quality of life, there must be some much larger imaginable population whose existence, if other things are equal, would be better even though its members have lives that are barely worth living.”

The supposed repugnance of this conclusion need not be conceded. The religious believer who regards suffering as freighted with potential moral purpose will have a very different reaction to a phrase like “barely worth living” than the typical secular utilitarian. The world of one hundred billion people who suffer tribulations might produce more saints; the world of ten billion people enjoying unparalleled hedonic pleasures might be under divine judgment.

Yet in framing the choice to have more kids as something that we should favor only within reason, aren’t we tacitly embracing some version of Parfit’s thesis – in the sense that for ourselves, we assume that there exists some family size whose possible tribulations exceed the good of an extra human being’s existence? Aren’t even we, the relatively fertile, minimizing our obligation to children yet unborn?

Perhaps medieval categories can help us. Perhaps we can say that the unique sacrifices required of parents – and let’s be clear that they’re required of women more than men – make the absolute case for children a counsel of perfection, a marital equivalent to the chastity and poverty and obedience demanded of members of consecrated life. The family that is open to new life unstintingly, eschewing not just contraception but any kid-spacing caution, is living a supererogatory life, going beyond the basic requirements of the moral law, in a way that we should admire without feeling condemned if we cannot do the same.

Just how many kids would count as supererogatory under this moral theory is another question. Kid-spacing caution was invented long before the 1960s, but clearly people in the past wouldn’t have regarded four or five kids as some sort of heroic, saintly, half-mad effort.

On the other hand, we shouldn’t overestimate the gulf between past and present either. People in many premodern societies married later than historical clichés suggest, and infant mortality rates meant that how many kids you bore was tragically different from how many kids you raised. Raising five children to adulthood would have been very normal in, say, seventeenth-century New England, but raising a Quiverfull-style dozen would have been exceptional even then.

The goal should be to help more families have the kids they already say they want.

Since my wife and I obviously did some spacing of our children, I’m aware that the decision to have only a “reasonable” number can be driven by all kinds of non-saintly, self-justifying considerations. But the idea of reasonability definitely influences how I think about persuading other people, my more secular neighbors especially, that more kids would be better. I don’t expect America to suddenly become filled with ten-kid families driving hulking vans. Rather, in a rich society with a plunging birthrate, the plausible goal should be to help more families have the kids they already say they want, meaning not six or eight or ten, but just one more – the kid who requires a new car seat and maybe a new SUV, the kid they feel like they might be able to afford, the kid you can feel pretty sure they won’t regret.

So what keeps us from that one-extra-kid world? One answer is that too many people fear that the repugnant scenario is here already – that overpopulation and climate change will between them usher in a future of unparalleled misery.

“Meet Allie, One of the Growing Number of People Not Having Kids because of Climate Change,” runs a recent NPR headline. Miley Cyrus recently declared her intention to refrain from procreating until somebody fixed the climate crisis: “I refuse to hand that down to my child.”

I’m not sure I believe her, though. I know there are some people who are sincerely child-free because they fear the ecological impact of overpopulation. This strikes me as a deeply mistaken approach to the climate crisis – above all, because any long-term solution will require exactly the kind of human ingenuity that a stagnant gerontocracy will tend to smother. But I can concede that it has some coherence, some altruistic pull.

Those I doubt are the people claiming that they’re refraining from having children for the kid’s sake, in a reversal of the argument for a moral obligation to have kids. Humankind has existed this long because people have borne children under radically difficult circumstances, amid famine, war, and misery on a scale we can’t imagine. Nothing in the potential life awaiting Miley Cyrus’s hypothetical daughter promises hardship remotely comparable to those ancestral burdens. And even if you think climate change will be truly apocalyptic, it’s no more threatening than the prospect of nuclear annihilation, which did nothing to prevent the last great Western baby boom.

No: In most cases, invoking climate anxieties seems more like an excuse, a gesture to ideological fashion, than a compelling ­explanation of low fertility. There has to be a deeper cause.

So let’s name three. First, romantic failure – not just in breakdowns like divorce, but in the alienation of the sexes from one another, the decline of the preliminary steps that lead to children, including not just marriage but sexual intercourse itself. Some combination of wider forces, the postindustrial economy and the sexual revolution and the identity-deforming aspects of the internet, are pushing the sexes ever more apart.

Second, prosperity, in two ways. One, because a rich society offers more everyday pleasures that are hard to cast aside in the way that parenthood requires. (Nothing gave me more sympathy for the childless voluptuaries of a decadent Europe than the first six months of caring for our firstborn.) Two, because prosperity creates new competitive hierarchies, new standards for the “good life,” that status-conscious people respond to by delaying parenthood and having fewer kids.

Finally, secularization – because even if it’s possible to come up with a utilitarian case for having kids, the older admonitions of Genesis appear to have the more powerful effect. The mass exceptions to low birthrates are almost always found among the devout, and the big fertility drop-offs in the United States correlate clearly with dips in religious identification.

The first of these three causes comes latest in history: the alienation of the sexes is mostly a post-1970s phenomenon, and previously any trend had run the other way. (More American women were married in the 1950s than in the 1880s.) Wealth and secularization, on the other hand, come in together centuries back, and entangle in all kinds of complicated ways.

In How the West Really Lost God, her provocative theory of secularization, Mary Eberstadt argues that the waning of the family led to declining religiosity rather than the other way around. Thus, for instance, the secularism of the Millennial generation might reflect their experience growing up as children of divorce, with weaker kinship networks leading to weaker ties to churches and other forms of communal life.

But I suspect it’s wiser to see the whole process as a set of feedback loops: the rich society creates incentives to set aside faith’s admonitions, which orients its culture more toward immediate material pleasures, which makes its inhabitants less likely to have children, which weakens the communal transmission belt for religious traditions, which pushes the society further along the materialist-individualist path.…and at a certain point you end up, well, here, with unparalleled prosperity joined to seemingly irresistible demographic decline.

So how might it be resisted? One answer is the kind of self-consciously reasonable vision I’ve already invoked – the push to just get back to replacement-level fertility, the push for one-extra-kid for families on the fence. The hope would be that the car-seat economists are right, and that simply by making family more affordable – reducing the cost of childcare or of a parent staying home, reducing the cost of education, reducing the cost of home buying, and so on – you can change both the immediate incentives and the cultural expectations around having kids.

Even if you think climate change will be apocalyptic, it’s no more threatening than the prospect of nuclear annihilation, which did nothing to prevent the last great Western baby boom.

The more it seems affordable to have a third or fourth child, in this hopeful theory, the more relaxed the whole culture might become – with less shaming of the fecund poor, less eyebrow-raising at large families in the upper middle class, and a lot more leniency for parents towing their broods on cross-country flights.

The more you deliberately organize institutions around supporting families, the more children would seem like a complement to education and opportunity rather than a threat. And the more you take family formation seriously as a policy goal, the more you transcend certain fruitless culture wars, and move toward a world where more mothers work part-time or stay home while their kids are young and more fathers play the paternal role that made possible not just Ruth Bader Ginsburg’s career, but Amy Coney Barrett’s as well.

I have some hope in this vision, in part because I move back and forth between secular and Catholic worlds – from contexts where we’re an oversize family to contexts where we’re below-average wimps. And so far in the secular world I don’t see all that much of the judging and hostility that some parents of large families report. (Though maybe the judging only kicks in once you have five or six.) Instead, I see a certain amount of friendly admiration, joined in people older than us to a mild I wish we’d had three instead of two regret.

Meanwhile, from the strange worlds of mommy bloggers and Instagram influencers all the way up to the Duggars of TLC, our pop culture manifests at least as much fascination with large families as it does with overpopulation fears. Maybe this fascination is itself a symptom of ill-health, a weird voyeurism about something that should come naturally. But at the very least it’s an homage that sterility plays to fecundity, and a signifier that there are lots of people who might have more kids if their situation felt slightly different, if economic pressures changed and cultural expectations altered with them.

Again, that’s what I’d like to believe can happen. But there are still times, many of them featuring the overwhelming exhaustion you feel at the end of a professional-parental day, I think that no, to get lots more people to sign up for this kind of lifestyle, you would need something more than a “parenting more than two kids: it’s more feasible than you think!” pitch. You would need our society to become dramatically unlike itself, ordered to sacrifice rather than consumption, and to eternity rather than what remains of the American Dream. You would need not change on the margins, but transformation – probably religious transformation – at the heart.

Certainly you can see the possible limits of policy tweaks and cultural nudges in the experience of other countries. The rich society that fully acknowledges an obligation to the unconceived may not exist, but many societies, European and Asian, do much more to support parents than the United States. And their results are not overwhelming: at the margins, policy can encourage births, but usually that means going from 1.4 kids per woman to 1.55, or 1.7 to 1.8 – gains that are fragile and easily swamped, both by specific events (like the Great Recession or the coronavirus) and by larger trends like the continued retreat from marriage and intimacy.

For the average sinner, life with children establishes at least some of the preconditions for growing in holiness.

So perhaps a greater cultural change in what we want is needed, even for a goal as modest as a fertility rate that matches our professed desires. And this change might not actually start with (even if it would necessarily include) a renewed sense of obligation to generations yet unborn. Instead, it might start with what we the living want and seek out for ourselves.

The libertarian economist Bryan Caplan once wrote a book called Selfish Reasons to Have More Kids, which falls mostly into the nudging sales-pitch category: it’s a list of reasons why having a big family is more compatible with normal late-modern ideas of fulfillment than many people think.

The deepest reason to have more kids, though, is self-centered in a radically different way. It’s that if you don’t feel cut out for spiritual heroism, if you aren’t chaste or poor or particularly obedient, if you aren’t ready to be Mother Teresa – well, then having a bunch of kids is the form of life most likely to force you toward kenosis, self-emptying, the experience of what it means to live entirely for someone other than yourself.

This can circle back to egotism, admittedly, for people who make idols of their children or practice a ruthless selfishness toward everyone outside the charmed circle of their household. Jesus called us to leave behind fathers and brothers for a reason: it’s still holier to be Francis of Assisi than a dad.

For the average sinner, though, for me and maybe for you, life with children establishes at least some of the preconditions for growing in holiness, even if there’s always the risk of being redirected into tribal narcissism. If I didn’t have kids there’s a 5 percent chance that I’d be doing something more radical in pursuit of sainthood; there’s a 95 percent chance that I’d just be a more persistent sinner, a more selfish person, because no squalling infant or tearful nine-year-old is there to force me to live for her and not myself.

But the idea of parenthood as enforced kenosis is very different from the idea that having more kids is swell and good and all-American. The large family as a spiritual discipline, children as a life hack that might crack the door of heaven – if that’s the worldview required to make our society capable of reproducing itself again, then we’re waiting not for child tax credits, better work-life balance, or more lenient car-seat laws, but for a radical conversion of our hardened modern hearts.