One has to go out of one’s way in Denmark to find a synagogue to terrorize—the country has only a few thousand Jews. And one has to go out of one’s way in France to find a kosher market to attack.

The terrorizing of the grocery in east Paris, where Amedy Coulibaly killed four people in January, all of them Jews, was not a “random” act of violence, as President Obama oddly suggested. Nor was the February shooting of Dan Uzan outside a Copenhagen synagogue. Nor was there randomness last year in the killing of four people at a Jewish museum in Brussels or in the murder of a rabbi and three children at a Jewish school in Toulouse. A vicious anti-Semitism persists on the streets of Europe as well as in the Middle East and on the Internet.

Is anti-Semitism on the rise, as many claim? Anti-Semitic crimes and attitudes are hard to quantify, and data vary from region to region. Attitudes of the general population may become more benign while violence perpetrated by a hard-core minority increases. Some studies show that the number of anti-Semitic incidents declined in parts of Europe in the decade before 2013 but has shot up of late. In the United States, home to 70 percent of the world’s Jews, the number of anti-Semitic incidents has held steady or declined in recent years.

Opposition to Israel’s occupation of the Palestinian West Bank goes hand in hand with much anti-Semitic fervor, especially in the Middle East, but it doesn’t account for all of it. Anti-Semitism in the Middle East, mostly imported from Europe, predates the 1967 occupation by several decades. And Israel’s policies are not made in Copenhagen, Paris, or Brussels.

Jonathan Sacks, former chief rabbi of Great Britain, wrote recently that virulent anti-Semitism arises when defeated and humiliated people seek an enemy to blame for their circumstances. That helps explain its rise in a defeated Germany after World War I as well as in the Middle East following the collapse of the Ottoman Empire.

The irrational, hateful trope of anti-Semitism—“the Jews are to blame”—has staying power. Yet its expression usually has a local dimension: the hatred serves as a calculated political diversion (as in some Arab states) or as a perverted expression of disenfranchisement (as with some Muslim immigrants in Europe). Such discriminations don’t change the maliciousness of anti-Semitism, but they help in determining causes and assessing how its appeal may be undermined.

Anti-Semitism flourished in the United States a hundred years ago. Jews faced widespread discrimination in employment, housing, education, and social clubs. But over the years courts dismantled barriers and civil rights watchdogs raised awareness, and Jews entered the social and economic mainstream. A Pew study last summer found that Jews are the religious group viewed most favorably in this country. The recent record of this country is far from unblemished with regard to anti-Semitism, but its history offers some hope that this malignant hatred can be tamed.