Nikolas Cruz, accused of killing 17 people in the Parkland, Fla., high school shooting, appears in court Feb. 19 for a status hearing in Fort Lauderdale, Fla. (Mike Stocker/South Florida Sun-Sentinel/AP)
Jennifer Vannette is a graduate from Central Michigan University, recently earning her PhD in U.S. History with an emphasis on 20th century human rights.

People across the political spectrum agree on one thing in the wake of mass shootings: the need to keep people with mental-health issues from acquiring guns. After all, they reason, a person who commits a mass shooting cannot be mentally sound.

But mental-health experts have warned against this reaction. Jeffrey Swanson, a Duke University professor of psychiatry and behavioral sciences, has argued that mental health has become a “scapegoat” that prevents a more “comprehensive discussion about how to prevent gun violence.” Emma McGinty, professor of health policy at Johns Hopkins University who wrote a study on mental illness and gun violence, concluded that only 4 percent of those who commit gun violence had a diagnosable mental illness (schizophrenia, bipolar disorder or depression). Red-flag behaviors such as anger management or substantive abuse, she reminds us, are not the same as clinically diagnosable mental illness.

Blaming mental illness has become a justification for offering expanded access to mental-health care as the main solution for preventing such crimes. Yet, the data simply doesn’t support this conclusion. The majority of mass shootings are perpetrated by white men — the demographic in the United States that reports the lowest rates of mental illness while having the highest access to health care, according to the National Alliance of Mental Illness (NAMI). In short, the best evidence we have is unequivocal: It’s not mental illness driving most mass shootings.

So, banning mentally ill people from purchasing guns is not the solution to mass violence.

In fact, this policy conversation distracts us from addressing  the real underlying cause of mass violence: ideology. When someone’s guiding beliefs incorporate a conviction that their societal position is threatened, ideology can become violent, resulting in catastrophe. Studying and publicizing the ideology driving mass shooters is critically important. Indeed, history has shown that it is the only way to spur the cultural changes necessary to reduce violence.

Mental illness has long been invoked as a justification for mass violence, disguising the darker ideology fueling it. Activist and journalist Ida B. Wells worked to end lynching, a common form of mass violence at the turn of the 20th century. She called attention to the systemic nature of racial violence. But to do so, she had to dispute claims that lynching was a product of mental illness.

In a speech delivered in Chicago in 1900, she said: “Our country’s national crime is lynching. It is not the creature of an hour, the sudden outburst of uncontrolled fury, or the unspeakable brutality of an insane mob. It represents the cool, calculating deliberation of intelligent people who openly avow that there is an ‘unwritten law’ that justifies them in putting human beings to death without complaint under oath, without trial by jury, without opportunity to make defense, and without right of appeal.”

In other words, it wasn’t mental illness that led to lynching. It was ideology.

Unmasking this reality was central to Wells’s anti-lynching mission. Although people of other ethnicities were also lynched, the main motivation behind the practice was to draw a clear distinction between whites and nonwhites and to use terror to enforce the racial hierarchy that limited political participation and economic independence for African Americans. According to the Tuskegee Institute, an estimated 3,445 African Americans were lynched between 1882 and 1968. Lynchings were public spectacles, ingrained in a culture that prized white supremacy. People took grisly souvenirs and posed for pictures with the tortured bodies.

Such acts were not a product of a few deranged people overcome by temporary insanity. They were part of a broader culture, and were generally tolerated by the government at all levels and accepted by white America.

The 20th century also witnessed another shocking form of mass violence: the Holocaust. As Benjamin Ferencz prosecuted the Einsatzgruppen — killing squads who rounded up Jews, Roma and communists from behind German combat lines, shot them to death and then unceremoniously dumped their bodies into mass graves — he emphasized that it was important to understand that the perpetrators were not “wild, raving maniacs.” They were not suffering from mental illness. They were instead driven by a twisted ideology.

“They justify it as necessary to protect their own conception of what the world should be like,” Ferencz explained. For Nazis, that ideology was one of a master race, which Adolf Hitler had promoted as a sacred concept. By doing so, he helped to justify and even dignify the use of genocide in the minds of his followers.

The Einsatzgruppen acted in a logical manner based on their conviction that their own place in society was threatened. It wasn’t a mental-health issue; it was an ideological issue. Ferencz believed in the importance of exposing the underlying cause of the systematic violence perpetrated by the Nazis so the international community could revise criminal law and work for prevention.

In the wake of the Holocaust, this understanding led to new international human rights agreements, and following years of work by civil rights activists, the United States eventually adopted hate-crimes laws to aid the investigation and persecution of bias-prejudiced violence.

This is the challenge we face today: understanding the ideology behind these mass shootings so that we can prevent them. Some mass killers make it easy for us to discern. Dylann Roof, who killed people attending a Bible study group at a historic black church in Charleston, S.C., said: “Somebody had to do it … black people are killing white people every day. … What I did is so minuscule compared to what they do to white people every day.” His ideological view of the world has allowed him to rationalize murder.

In other cases, it’s less clear. We still don’t know what motivated Las Vegas shooter Stephen Paddock.

For many people, it is inconceivable that someone in good mental health could shoot schoolchildren, randomly fire into a crowed music venue or murder people gathered in Bible study. Yet the evidence suggests that mental illness should not be the focus of our debates on how to end mass shootings.

The examples of Ida B. Wells and Benjamin Ferencz illuminate the power of exposing the ideologies that help individuals rationalize mass violence. Although they did not eliminate all mass violence, their activity led to new laws, new human rights agreements and a change in the public discourse. To learn from their examples, we need to study the ideological underpinnings of mass shooting to find the way forward.

That means focusing on why so many men — and men are statistically far more likely to be the shooter, the recent female shooter at YouTube headquarters notwithstanding — feel that their place in society is threatened.

Mass shooters appear to act in a calculated manner based on their feelings of invalidation. Despite media claims that shooters are lone wolves, many have found affirmation through Internet sites that claim that minorities or women are to blame for loss of male status. Social psychologists have searched for answers by examining links between economic downturns and racial or other violence, and the results are mixed. However, they have noted that actual loss of economic, occupational or social status matters less than the perception of that loss.

At Nuremberg, Ferencz wanted the international community to face the systematic nature of the violence so that everyone would understand the role of ideology. He said, “you cannot kill an  idea … you can only change it by a better idea.” To correct fears with a new perspective, society needs mediators. In the past, politicians and other elites have served in that role. Today, however, our leaders are stoking political division, so we must find new mediators to soothe those who feel disenfranchised.