For most social issues that the Supreme Court decides, arguing tends to die down after a couple of years. We’ve seen this even when the initial level of disagreement was intense at the time of the decision, as it was with, say, interracial marriage and school segregation. With other issues, such as gay marriage or the legalization of contraception, millions of people had already changed their minds long before the court announced its decision, and so previously unthinkable policies quickly became widely accepted actions, smoothed over by widespread grassroots support. But almost half a century after Roe v. Wade, abortion remains a hot-button issue in American politics.

It factors heavily into presidential elections, including the most recent. During the 2016 campaign, Donald Trump promised the landmark Supreme Court decision would “automatically” be repealed if he was elected president and got to appoint justices to the high court. The exit polls found that a president’s appointments to the Supreme Court were “the most important factor” in the decision for more than 1 in 5 voters—and voters who felt that way supported Trump over Hillary Clinton, 57 to 40 percent. This helps explain why evangelicals could vote for the twice-divorced Republican candidate (though the reasons go well beyond his position on abortion). Trump’s subsequent successful nomination of Neil Gorsuch is seen by his supporters as one of the clearest evidences that he has kept his campaign promises, and now, with Justice Anthony Kennedy’s retirement, he’s gotten the chance to propose a second justice. And Brett Kavanaugh seems ready to cast the deciding vote in overturning Roe.

The intensity and tenacity of the abortion debate makes it unique in recent American political history. Despite the bitterness of the debate, Americans’ opinions on the abortion issue have barely budged in more than four decades. In 1976, 75 percent of Americans believed abortion should be legal under at least some circumstances and 22 percent believed that it should be illegal under any circumstances. In 2018, the figures were 79 percent and 18 percent respectively.

The very characteristics that lead people to become conservative lead them to oppose the availability of abortions.

On the surface, the stalemate is the consequence of the issue’s obvious moral implications (“killing a human being” on the one side, the human rights of the mother on the other). It also reflects disparate religious beliefs and deeply rooted and opposing reactions to the rise of feminism and changes in the status of women. Each side seems increasingly immune to the counterarguments to its own case.

And yet, the fact that the numbers have not strayed suggests a larger truth about the state of the abortion issue in America today. It’s not just the way the issue intersects with the idea of morality. The partisan positions on abortion are tightly linked to their adherents’ general political positions. Support for the “right to life” and the “right to choose” align closely with overall political beliefs: 71 percent of conservative Republicans say abortion should be illegal in most or all cases, while 91 percent of liberal Democrats say it should be legal in most or all circumstances.

Why do conservatives generally oppose and liberals generally support abortion rights? Because the very characteristics that lead people to become conservative lead them to oppose the availability of abortions, and the very characteristics that lead people to become liberal lead them to demand the right to choose. Both opposing political views and the conflicting views of abortion directly or indirectly reflect deeply rooted psychological, psychosexual, and moral differences between their proponents, factors that will provide adequate fuel to any argument. And this makes the whole complicated situation even more intractable.

Start with the differing psychological and moral needs of the two sides. A large body of research shows that conservatives and liberals tend to differ in personality and in moral values. These are not absolute differences, of course, but on average the political differences are associated with differences in personality and patterns of moral reasoning.

With respect to personality traits, for example, many people, more typically on the right politically, are intolerant of ambiguity and experience change itself as a threat. They feel discomfort in a world in which there is moral ambiguity and a need to make choices. To people for whom choice itself is the issue, the “right to choose” has little appeal as an argument.

Conservatives also tend to show higher levels of dogmatism and cognitive rigidity than liberals. The belief that compromising with political opponents puts one on a slippery slope leading to betrayal of one’s own side comes easily. And conservatives tend to perceive the world as more dangerous than liberals do. They are more likely to accept arguments that abortion is dangerous to the physical or mental health of women, despite the fact that the overwhelming weight of the evidence is that the claim has no merit.

As for the differing bases for making moral judgment, Jonathan Haidt and his collaborators have argued that there are five distinct psychologically based foundations for making moral judgments. We detect and react emotionally to issues related to (a) not doing harm and providing care; (b) ensuring fairness and reciprocity; (c) maintaining loyalty; (d) respecting authority and tradition; and (e) maintaining “purity and sanctity” (i.e., not violating the sense of what is sacred and what is morally abhorrent).

Haidt has found that political liberals primarily rely on the first two foundations in making moral judgments, while political conservatives generally rely upon all five. As a result, the two groups have different grounds for deciding whether a particular behavior is “immoral.” The liberal moral argument for abortion rights is based on the importance of not doing harm (e.g., protecting women’s health and well-being) and on fairness (i.e., protecting women’s rights). The persuasiveness of these arguments to conservatives is lessened by the latter’s insistence on also using tradition and purity as bases for judgment. Conversely, the conservative argument against abortion, primarily rooted in a morality that is based on respecting tradition and maintaining purity, makes little sense to liberals.

Yet another personality difference between conservatives and liberals is in patterns of thinking. Conservatives tend to show higher levels of dogmatism and dichotomous (black-and-white) thinking. Thus, the idea of a fetus that both is and is not a person is problematic, and the necessity for an individual to make choices about the life or death of a fetus is unbearable.

Proponents and opponents of abortion rights also have different perspectives on sexuality. Both left and right alike have long understood that sex and lust and love can be personally and socially disruptive forces. At an individual level, easy access to abortion (like access to contraception) makes it easier for women to express their own sexuality without fear of pregnancy. This has the potential to disrupt traditional family relationships and is a direct assault on conservative traditionalism and respect for (male) authority.

Almost by definition, conservatives, who value tradition and stability, fear such disruption, while liberals are more open to it. Thus, for conservatives, anything that seems to promote freer sexual behaviors becomes a major source of anxiety, to be rejected. Abortion seems to open the door to promiscuity and moral decay, and perhaps to political upheaval, as well.

By contrast, even long before the emergence of modern feminism, for many on the left the “traditional” family has been seen as a source of oppression for women. Equally, a rigid sexual morality, partly rooted in Christianity, has been seen as a central element in maintaining repressive social arrangements in general. Sex radicalism has been an integral part of movements for women’s emancipation and freedom since the French Revolution. To much of the left, from Wilhelm Reich in the 1930s to the New Left of the ’60s and the women’s liberation movement and gay movements of the ’70s, liberating sex from repressive social and psychological forces has been seen as central to human liberation, to be welcomed, not feared.

The differing reactions to sexual behaviors has a racial dimension, as well. Lower status groups—gays and lesbian, blacks, Jews, immigrants, the poor—have often been seen as “hypersexual” or “carnal” by higher-status groups. Fears that immigrants were out-reproducing “white” people drove the eugenics movement of the years before World War II. Even today, the alt-right denounces the “carnality” of Jews.

In the Jim Crow South, lynchings were defended as preventing rape. Strom Thurmond, in his 1948 campaign for president, argued that “miscegenation” would undercut the separation of the races needed for “the protection of the racial integrity of the white and Negro races alike,” and White Citizens’ Councils in the 1950s blamed anti-segregation activity on “negroes of mixed blood.”

In recent years, poor women of color have been the overwhelmingly disproportionate users of abortion services. This appears to be especially the case in the “red” states. It is less socially acceptable to openly express racial and ethnic prejudice, today. Opposing abortion may serve as a more acceptable stand-in.

The rigidity of anti-abortion sentiments may also reflect sexual anxiety experienced at the individual level. Recall that strong anti-abortion beliefs are correlated with political conservatism. Conservative men show higher levels of sexual repression, reflected, for instance, in their greater preoccupation with sexual content in private internet activity despite their greater religiosity and in their greater conservatism with respect to sexual behaviors. For instance, conservatism is associated with a preference for traditional sex behaviors (e.g., missionary position sex), older age of first intercourse and fewer sex partners, fewer adventurous sexual behaviors (e.g., use of sex toys), and fewer risky-sex behaviors (e.g., sex with a stranger).

The intensity of the abortion debate is often seen as the result of its injection into partisan politics. But the argument is just as strong if we reverse it. American politics have become intensely partisan because of the links between political ideology and position with respect to abortion. It is impossible to separate the histories of contemporary conservatism and liberalism from the history of the abortion debate. Opposition to abortion has become an identifier of conservatism and of conservative identity, and conversely, support for reproductive rights has become an identifier of liberalism. To be conservative is to be against abortion; to be liberal is to be for women’s right to choose.

The commitment to these ideals might actually be getting stronger, not weaker. The move of anti-abortion religious conservatives—evangelical and born-again Protestants and conservative Catholics—into the Republican Party since the late ’70s is the central element in the history of modern conservatism. And over the past five decades, as Americans have become more conservative and liberals have become disempowered, liberals have had to cling harder to their beliefs. To compromise on issues such as abortion rights would be to give up one of the last vestiges of the beliefs that constituted them as liberals.

The intensity of the abortion debate is often seen as the result of its injection into partisan politics. But the argument is just as strong if we reverse it.

Political views reflect perceived self-interest and strengthen bonds with family, friends, and community. But they also reflect psychological characteristics and needs. A central link between personality and political views is “right-wing authoritarianism.” RWA is defined by authoritarian submission (submissiveness to authorities who are seen as legitimate in the society in which one lives), authoritarian aggression (general aggressiveness directed against deviants and out-groups), and conventionalism (adherence to the traditions and generally accepted social norms and a belief that others should be required to adhere to these norms). Both conservatism and anti-abortion attitudes have common roots in high RWA. (Both RWA and conservatism are also correlated with prejudice toward out-groups, e.g., blacks, Jews, immigrant, non-“traditional” women; support for conventional gender and family roles; narrow definitions of male/female roles; misogyny and devaluing women; conservative social mores; and anti-feminist attitudes, and a tendency to have punitive attitudes toward women who have had abortions. Conversely, both liberal politics and liberal views on abortion have common roots in low RWA.)

Both experiments and cross-national observations suggest that a sense of threat increases RWA in individuals. And over the past five decades, there has been a rise in social anxieties, reflecting changes in the status and roles of women and racial minorities, globalization and technological change, growing inequality and wage stagnation, and the direct and indirect impacts of neo-liberal governmental policies. These anxieties, via their impact on levels of RWA, explain the shift to the right, political polarization, and ultimately, the rise of Donald Trump, and why people hold on to anti-abortion views so strongly.

One counterpart to right-wing authoritarianism is liberals’ abiding faith in the values of the scientific revolution and the Enlightenment. For liberals, finding facts, pursuing knowledge, and trusting science are part of their moral system itself. Liberals view human nature as essentially good and believe that human history is a story of increasing freedom. As Martin Luther King Jr. famously put it, echoing the words of abolitionist and reformer Theodore Parker 100 years earlier, “The arc of the moral universe is long, but it bends towards justice.”

Conservatives, by contrast, tend to have a usually unspoken distrust of empiricism and reason themselves and, conversely, tend to embrace a system of knowledge and belief based on intuition and faith, and trust in revealed truth. (This distinction is at the heart of the partisan reactions to Kellyanne Conway’s celebrated notion of “alternative facts”). The mistrust of reason and “facts” has been embraced by today’s conservative movement.

The anti-abortion camp roots its understanding of truth in faith; the pro-choice camp roots its arguments in reason. But in a time when rationality, “truth,” and Enlightenment-derived ideas of human rights are under attack, the impact of these arguments on the former group is weak. Abortion remains a hot-button issue because it is deeply embedded into the very nature of both conservatives and liberals. When they speak to each other about it, they’re barely talking the same language. No wonder the debate has gone nowhere.