As dozens of Jewish New Yorkers gathered in Rabbi Chaim Rottenberg’s home to celebrate the seventh day of Hanukkah, a passerby spotted the Menorah, stopped, and walked toward the front door.

Worshipers had begun to filter into the synagogue next door for a holiday meal as 37-year-old Grafton Thomas barged into the home, pulled out a knife that looked “almost like a broomstick,” closed the door behind him, and said, “Nobody's going anywhere.”

He began to stab and slice at “everyone he could,” leaving one victim with wounds to the head, neck, back, and arm, and injuring four others. He then tried to enter the synagogue next door, but the congregants had heard the commotion next door and locked him out. Thomas fled the scene, and police later found him with stains on his clothes, smelling of bleach, blood, and hate.

The attack lasted only two minutes, but it was brutal and all too familiar to New York’s Jewish community — a people that now live in fear on the streets they once claimed as their own. Saturday’s attack was the ninth that week.

And each one of the individual attacks bears certain similarities: the victims are almost always Hasidic or Orthodox Jews, the attacks are seemingly random, and the attackers' motivations are labeled “unclear,” just as Thomas’s were.

But Thomas’s motivations weren’t “unclear” at all, and his attack wasn’t random. He saw the Menorah and chose to enter that home and kill as many Jews as he could, simply because they were Jewish. It’s likely he had intended to attack the Jewish community at some point that night. He was carrying around a machete, for goodness sake.

For those unfamiliar with the history of anti-Semitism, Thomas’s attack might indeed seem random and even strange. Why would a man enter a Jewish home unprovoked just to kill? Why would a group of teenagers randomly beat a 65-year-old Jewish man and his 6-year-old son? Why would a crowd of spectators laugh as a young man poured his drink on a 25-year-old Jew in Brooklyn? Why would a woman begin hitting a 34-year-old Jewish mother with her purse as her children watched?

The frustrating thing about anti-Semitism is that it has no explanation. It makes no sense. We can't just explain it away, attribute it to a particular group, person, or political party, and look the other way. Anti-Semitism can't be fit into a box or tied to an ideology because it predates ideology, race, political structure, and just about every other hatred that has ever plagued this world.

Anti-Semitism tends to be more common among the extreme Left and Right. But that's because radicals on both sides of the political spectrum are simply taking advantage of a historical, and often socially acceptable, hatred. Just look at the situation in Europe. The shame of the Holocaust created a temporary reprieve, but now virulent hatred of Jews is once again common. No one blinked an eye when Italians protesting Gaza called for a boycott of Jewish merchants. Or when a popular French comedian introduced a new kind of Nazi salute. Or when a rabbi and his three children were murdered in their home in France. As of last month, about 1 in 3 Europeans admitted to holding some sort of anti-Semitic opinion.

Here in the United States, it seemed like we had rid ourselves of Europe’s hatred. But Thomas’s attack, and the dozens that occurred before it, are a painful reminder that we have not, and we will not until we admit what we’ve done to foster it.

We have created a political culture of apathy. Anti-Semites such as Al Sharpton and Louis Farrakhan have become normalized — so normalized, in fact, that prominent politicians and presidential hopefuls meet with Sharpton to seek his blessing.

Anti-Zionism and visceral hatred for Israel — one of the last Jewish safe havens in the world — is normal and often expected on the Left, especially on today’s college campuses. Anti-Zionism is not the same as anti-Semitism, but the two go together so well that the adherents of one usually can't pass it up. Anti-Semitic tropes are casually thrown around on college campuses, not just in alt-right online circles. In the very halls of Congress, they are declaimed by elected representatives of the people. And simple gestures — such as President Trump’s recent executive order extending civil rights protections to Jewish college students — are condemned as unnecessary, misplaced, and (get this) anti-Semitic.

I doubt that any of the factors I just named inspired or caused Thomas to enter a Rabbi’s home and stab five people. But it is a reminder that our words, actions, and policies create a context in which anti-Semitic rhetoric and violence find justification.

There will always be individuals looking for an excuse to hate, and unfortunately, Jews are often the target. Sometimes it is because of their ethnicity, culture, or faith, but oftentimes it is because “in the eyes of the anti-Semite, the Jew is … everything” and anything the “anti-Semite needs him to be,” as New York Times columnist Bari Weiss writes in her book How to Fight Anti-Semitism.

Anti-Semitism exists in part because we allow it to — because we read about these attacks, offer a few sympathetic remarks, and then return to life as normal. The media, too, has ignored this issue, as my colleague Seth Mandel pointed out on Twitter. And as a result, anti-Semitism has slowly become normal.

It is an old hatred, perhaps the oldest, and it cannot be allowed to spread any further. New York used to be safe; now, it is not. And it is incumbent upon each of us to stigmatize anti-Semitism, to reject it, and to create a culture that refuses to accept it in all of its forms.

This problem extends far past the Jewish community, and if we do not act now, it will leave a dark stain on our nation for years to come.