Few debates matter more to the West’s future than the widening divide between left and right over the simple act of having children. Inside an April pronatalism conference in Austin, the roster stretched from the more traditionalist Catherine Pakaluk to libertarian Bryan Caplan. Outside, left-wing protesters branded the gathering “neo-Nazi.” The answer to the question of whether children are worth having will shape everything from fiscal policy to cultural identity. The roots of the quarrel are worth tracing.

That even childbirth now falls under the old slogan “the personal is the political” may shock. Yet it follows naturally from each camp’s bundle of larger ideological commitments. For conservatives, increasing fertility in the West is part of the defense of its civilization. Europeans and other groups that were at its heart are no longer reproducing themselves. Across the OECD, the total-fertility rate has slid to 1.5 children per woman; in Italy and Spain, it hovers near 1.2, and even in the United States, the latest CDC release puts the rate at just 1.63—far below the 2.1 replacement benchmark. For many conservatives, every newborn is a vote that the West remains worth inheriting.

The religious right also has theological reasons for favoring procreation. The Abrahamic religions share the injunction to be fruitful and multiply. All greatly value motherhood. The most iconic image in Western art—the Madonna with Jesus—is an encomium to the pairing of woman and child. Bearing children affirms the belief that God made a good world. We may fall short of that promise, but the act itself testifies to the cardinal virtue of hope.

Natalism also gains support from the right’s rawer political calculations. The crisis of fertility among its native populations contributes to the graying of population and the reduction of its workforce. Yet all Western democracies have pay-as-you-go social security systems dependent on a high ratio of workers to retirees. These brute facts create a fiscal dilemma. Across Europe, leaders duck pension reform but recognize that raising already high taxes would strangle growth. In the United States, leaders likewise dodge entitlement reform and propose hiking taxes only for the top 2 percent. Soaking the rich will not put much of a dent in our record peacetime debt. The obvious solution is to increase the worker-to-retiree ratio by making the population younger. Conservatives would rather accomplish that through increasing birth rates rather than massive increases in immigration. The latter is thought to threaten the distinctive national cultures they value and destabilize politics.

The left does not share these positive reasons for supporting fertility. It does not think Western civilization is one that necessarily should be continued, and is generally indifferent to religion. But the left has other reasons of its own to resist natalism.

One is feminism. Many feminists have persistently argued that social structures keep women from being equal to men in achievement—in the arts, in the sciences, and in business. One of the greatest impediments is the family structure where women undertake more unpaid labor than men, particularly in raising children. Increasing child-care subsidies and supporting early education might look like a fix. Yet nations that lavish money on day care still see women falling behind men in pay and prestige. Once they have children, most women still want to spend more time nurturing than men. Thus, the only way to prevent women from becoming parental specialists is not to become parents.

Another reason that some on the left are not enthusiastic about bringing children into the world is the environment. More people create more pollution and burden the Earth’s biosphere. In some more radical views, new generations are likely to be despoilers of the natural wonders of the earth that need preservation.

If low fertility is causing a fiscal and economic crisis, in the West, the left’s solution is to fling open the borders to more migration. The left believes that foreigners have as much right to enjoy the higher living standards in the West as those who already live there. Indeed, among some more radical voices, they may often have a greater moral claim, because their poverty is caused by the West’s colonialism. The left welcomes the multicultural transformation of the West that great inflows will bring. “Diversity is our strength” is its mantra.

To be fair, the left is no monolith; plenty of progressives still toast big families. Yet, as with transgender orthodoxy and erasure of national borders, it is the activist vanguard that writes the party script. Their chill toward procreation flows from faculty lounges to platform planks, then filters down to voters who sense disdain. Elite ideas tug Democrats leftward long before the rank-and-file notices

It might be argued that what is really depressing fertility is not ideology but economics. Housing costs, student-debt burdens, and delayed marriage no doubt matter. But citizens of the West, including the young, are far wealthier and live far more comfortably than in past eras, where fertility rates were much higher. Medical assistance, like IVF, increases the effective reproductive span of women. But Sweden and Hungary show that baby bonuses and family leave pad wallets, not bassinets. Values and culture, not subsidies, rock the cradle.

The contest over childbearing carves a deep rift in today’s political landscape. The left-radical position is likely to damage their party’s political standing. The impulse to have children is deeply ingrained; indeed, from an evolutionary perspective, children are the goal of human life. It is true that contraception has cut the close link between sex and reproduction, but human nature prompts the desire for children in ways other than through sexual desire. Children are cute, and there are few other ways most of us can leave an enduring mark on the world. Thus, this latest left position is going against the human grain.

Moreover, the ideological reasons for skepticism about bringing children into the world may be seen by many as the reductio ad absurdum of left positions. If feminism means that women must avoid having children from being beguiled into an unequal relation with men, feminism then demands that women give up a great source of human fulfillment to be true feminists. If environmentalism opposes the propagation of humanity, such environmentalism seems to prefer the rest of the natural world to the one animal that can see it whole. Treating immigration as a stand-in for native births slips into oikophobia—those who, in Gilbert & Sullivan’s jab, “praise, with enthusiastic tone … every country but their own.”

History, however, shows that creeds hostile to the cradle soon confront their own demographic sunset. The Shakers—an eighteenth and nineteenth millenarian sect who enjoined celibacy on their adherents—are unsurprisingly no longer around. While children do not directly inherit their parents’ political beliefs, there is a correlation in the ideology between parent and child. A growing distaste for having children on the left will, other things equal, push the nation toward the right.

In terms of contemporary politics, the stance against children is sure to continue to push the so-called “normies” (this generation’s echo of the “silent majority” of the 1960s) away from the left. The “normies” now shaping American elections are the large, loosely organized bloc of middle-of-the-road voters—disproportionately non-college, suburban or ex-urban, and culturally conventional—who recoil from both progressive identity politics and hard-right theatrics. Their irritation with the left concerning issues such as transgender athletics or “defund the police” policies stems from a mix of practical worries (fairness in sport and public safety), moral intuitions grounded in mainstream religious or communal norms, and a perception that progressive elites impose niche values without democratic consent. Outnumbering the zealots on both flanks, normies now choose who governs in close races.

Few positions will rile normies more than contempt for the desire to have children. Enthusiasm for having children has been a widespread and religious cultural norm for virtually all of human history. Skepticism of having children is the paradigm niche issue pressed by certain elites. A preference for immigrants over native children is an extreme version of open borders that normies also reject.

It is true that some of the pronatalism of the right may also be off-putting. Some celebrity advocates for more children hardly model the stable families most parents envision. Even the very name “natalism” can alienate ordinary people because it appears to create an odd term for something that comes naturally. Even so, the quirks of the famous and a pompous Latinate label will offend less than open hostility to child-baring.

Whatever one thinks of baby bonuses or child tax credits as policy matters, the fertility fight lays bare the deepest fault line in modern politics. The left, increasingly doubtful about the worth of the West, treats birth as a lifestyle choice to sometimes be discouraged. The right regards it as constitutive of human flourishing. The quarrel over the cradle is thus no social-policy sideshow. It is the distilled essence of two rival creeds. Tell me where an ideology stands on the need for babies, and I can tell you where it will stand on much else.