I was listening to the BBC’s The Arts Hour when the host introduced the Algerian singer-songwriter Souad Massi. Forced to leave her homeland after receiving death threats, she now lives in Paris. Her latest album, Zaghate, explores conflict, war, and injustice. While speaking about the album, she said something that made me stop in my tracks.

“When you don’t want to make an effort to know someone, you develop a certain hate, and this hate becomes a virus.”

In one sentence, she explained something philosophers, historians, and psychologists have wrestled with for centuries.

Souad Massi reminded me of Chinua Achebe, Alexandre Dumas, and countless others who have tried to shed light on the core causes of humanity’s greatest atrocities. Though they approached the question from different directions, they arrived at much the same conclusion: hatred grows in a space where understanding has been pushed out.

As part of the animal kingdom, our first instinct when confronted with a stranger is not to trust and embrace. Long before civilisation, we developed a survival instinct that depended on caution. The unfamiliar is perceived to be dangerous. That instinct served our ancestors well when predators lurked in the forest beyond our huts. But what helped us survive as animals can diminish us as civilised human beings.

For all intents and purposes, every encounter with another person starts from a place of ignorance. We typically know nothing about their history, fears, dreams, or circumstances. They could be similar to ours or different. Whatever it is, we face a choice. We can make the effort to understand, or we can remain comfortably ignorant.

If we have to share the same space, that choice makes all the difference.

While the choice of learned understanding leads to mutual respect and building bridges in a shared space, the choice of comfortable ignorance leads to increased suspicion and building walls.

When we refuse to understand, ignorance prepares room for fear. And when fear is allowed to fester, unchallenged, it transforms into hatred. In the dark chambers where hatred resides, it nourishes itself in the filth of negativity until it reemerges in the form of violence.

Souad Massi called hate a virus because that is exactly how it behaves.

Like every virus, it needs a host. Ignorance is its favourite host. Fear provides the environment in which it can incubate. Like a virus, hatred spreads through communities, families, religions, and nations, infecting those with compromised immune systems and those considered healthy. Some may never know they have become infected until it manifests in them in the form of violence. That is why, after each genocide, a group of people who participated always wonder what got into them.

History is littered with this pattern of behaviour, resulting in devastating outcomes.

Whether in the Holocaust, the Armenian Genocide, King Leopold’s Congo Free State, the Rwandan Genocide, or the starvation that accompanied the Biafran War, the script was remarkably similar. Long before the killing began, people had already stopped seeing one another as individuals worthy of understanding, preservation, and redemption. They have conveniently condemned their fellow humans to lower categories, disgusting stereotypes, mere enemies, vermin, infidels, outsiders, or obstacles to the mission of the self-arrogated superior group.

Mass murder always begins in the mind long before the first machete is sharpened, raised, and landed on a fellow human.

Modern psychology helps explain why this happens.

Hatred often serves as an alibi. It allows us to blame others for failures we would rather not confront within ourselves. It is easier to point at a convenient enemy than to examine our own shortcomings. Once we settle on someone to blame, our minds go to work reinforcing and protecting that judgment. We search the dark corners of the world for evidence that confirms what we already believe, while dismissing everything that contradicts it.

Today’s social media-driven world defends our conclusions even when the methodology we used to arrive at them is wrong. It cheers as we worship at the altar of algorithms despite knowing that algorithms reward outrage over nuance. Every click deepens our position in the trench, bombarding us with voices that echo our prejudices while shutting out those that might challenge them. We submerge into the rabbit hole of our battalion, where we add concrete to the wall separating us from people who are different.

Echo chambers do not merely comfort us; they reinforce our opinions and strengthen identities. Before long, disagreement jumps from being an intellectual exercise to a severe personal attack.

Hatred is among the strongest emotions human beings experience. Interestingly, its equal and opposite is love.

It takes something profound for a person to say sincerely, “I love you.” It also takes something profound to say, “I hate you.”

Both emotions consume the people who hold them. Both demand commitment to burn something in us to keep the emotion going. Right there, they shape what we become. There is no way to love or hate without spending a little of ourselves.

The difference is that love requires us to see another person’s humanity, while hatred sets the denial of that same humanity as its first condition.

That may be why hate spreads so easily, while love takes a little more time. Understanding demands effort, while hatred asks only that we join the mob.

In a few generations, victims of hatred from a few generations ago turn around to become perpetrators.

We see these painful reminders in conflicts around the world today, where memories of yesterday’s suffering are deployed to justify today’s cruelty.

The virus changes hosts, but its nature remains the same.

The ability or refusal to understand others has never been confined to any race, religion, nationality, or class. Someone may spend a lifetime in one of the world’s most educated societies and remain slaves to humanity’s oldest instinct.

It is astonishing how often we encounter intelligent, accomplished people who still believe sweeping generalizations about entire groups of human beings.

Perhaps they never encountered Alexandre Dumas, who observed:

“All generalisations are dangerous, even this one.”

Or perhaps Dumas feels too distant.

Surely, though, they might have stumbled upon Chinua Achebe’s timeless warning:

“Stereotypes are not necessarily malicious. They may be well-meaning and even friendly. But in every case, they show a carelessness or laziness or indifference of attitude that implies that the object of your categorisation is not worth the trouble of individual assessment.”

Achebe’s insight reaches beyond prejudice. It identifies its root.

Hatred often begins not with malice but with intellectual laziness, premised on an unwillingness to do the difficult work of seeing another human being as an individual rather than a category.

In the face of unpalatable ideas, we often resort to censorship. We silence offensive voices, hoping hatred will disappear with them.

History suggests otherwise.

Suppressing genocidal opinions rarely destroys them. More often than not, it drives them underground, where resentment gathers strength like a hurricane until the opportunity for revenge finally arrives.

History suggests that bad ideas are rarely defeated by silence alone. They are more often weakened when exposed, challenged, and stripped of their moral disguise.

And when an idea needs disinfection, or a healthy dose of oxygen, we make sure it gets exactly that.

To understand does not mean to agree. It means being curious, open-minded, and asking why things are the way they are.

When we make the effort to understand another person’s history, fears, aspirations, and circumstances, we often discover that our worst assumptions are mere exaggeration. At that point, doors we thought were permanently closed slowly began to open. And that is when yesterday’s certainties disintegrate into mere questions. And certified enemies become human beings again.

If we get there, we experience the exhilarating feeling of growth. And we give others the space to grow beyond the stories our biased minds first told us about them.

Perhaps Souad Massi was right.

Hatred is a virus.

But every virus has a weakness that immunologists and virologists exploit to save humanity from extinction.

Rudolf Ogoo Okonkwo teaches Post-colonial African History, Diasporic African Literature, and African Folktales at the School of Visual Arts in New York City. He is the author of “This American Life Sef.” His latest book is “A Kiss That Never Was.”