Scholars in recent decades have tried to analyze and explain the origins of antisemitism, “the longest hatred.” Yet we still have no consensus.

Did the antisemitism of the West originate with the classical Greeks and Romans who saw the Jews as misanthropic enemies of humanity? Or did it come from Christian supersessionism, the “replacement theology” that argues that Jews have been replaced by Christians as God’s chosen people and are now accursed for not following God’s plan for the world? As for the different forms of antisemitism in the 20th and 21st centuries, are they natural outgrowths of pre-modern antisemitism or are they radically different?

One of the most prolific and skilled of these antisemitism scholars is Hebrew University of Jerusalem professor Robert Wistrich. Much of his early writing centred on antisemitism in the contemporary Arab world. Two years ago he produced a magnum opus on the history of anti-semitism, A Lethal Obsession: Antisemitism from Antiquity to Global Jihad. Now he has published a book of more than 600 pages, titled From Ambivalence to Betrayal: The Left, the Jews, and Israel.

Wistrich’s latest book is based on careful, meticulous scholarship and cogent analysis. He explains the potential for tension between modern Zionism and modern left-wing thinking, both of which arose in Europe in the 19th century. Many thinkers were convinced that a “Jewish problem” existed, and that it was not clear where Jews could fit in in a radically different modern world.

Zionists tended to argue that there was no hope for Jewish integration in Europe; Jewish national autonomy in the Land of Israel was the only answer. Leftists, on the other hand, who had ambivalent, or worse, attitudes to nationalism, thought that encouraging Jewish nationalism was counter-productive to the goals of socialism. Many of them believed that the radical reorganization of European society that they advocated would solve the Jewish problem once and for all.

Wistrich, of course, acknowledges that even in the 19th century some Jews (and some gentiles) successfully combined Zionism with left-wing ideology, just as some do today. But his basic premise is that today’s leftist anti-Israel ideology that is so often mixed with elements of antisemitism can be at least in part traced back to the original tensions between these movements.

One of the most disturbing chapters describes in detail some of the worst types of anti-Zionism and antisemitism in the radical left in contemporary Great Britain. As Wistrich explains: “It needs to be emphasized that this kind of new antisemitism in Britain is not exactly the same kind of hatred that prevailed in Europe 70 years ago. The complex multicultural society of Great Britain will not readily tolerate cries of Sieg Heil, jackboots, or the openly racist mythology that was irrevocably stained by the Holocaust… The spearhead of this [new] assault has been the ‘anti-racist’ left in Great Britain which now attributes to Jews and the State of Israel the worst sins of the West – racism, ethnic cleansing, ‘crimes against humanity’ and even genocide. This conscious attempt to ‘Nazify’ Judaism, Zionism and Israel deserves to be regarded as one of the most scandalous inversions in the history of the longest hatred.”

Another chapter shows how, against all reason, some radical leftists have made common cause with Islamists, united by their animus to Jews and Israel despite the fact that virtually all other parts of their ideologies are incompatible.

This book will be useful for scholars of antisemitism, but it appears that Wistrich has a political motive beyond the academy. In the introduction he writes, “This book goes to the heart of what has become a serious mental derangement in the hope that it might help the left… to regain their sanity.”

The way Wistrich presents his arguments leads the average reader who is concerned about antisemitism to conclude that the left constitutes the greatest danger. This is a common claim made by people with neo-conservative agendas. For example, in a series of tendentious articles on Jews, money and U.S. politics in the National Post this summer, Lawrence Solomon argued that Jews in the United States used to vote Democratic since they were convinced that the right was antisemitic. Now that rationale is gone since, he argues, much of contemporary antisemitism derives from the left.

But does it? The worst antisemitic episode of history, the Shoah, was perpetrated by a modern right-wing ideology, and right-wing antisemitism, especially on the radical right, is hardly a spent force. Even after reading this well-researched book I don’t know whether I, as a Jew, should be more afraid of the loony left or the radical right. And while I was convinced by Wistrich that the phenomenon of leftist anti-Zionism and antisemitism is worse than I had imagined, I still don’t know how much of the left is implicated. Is it five per cent, 50 per cent or 90 per cent? While I learned from this book that Holocaust denial or “Holocaust inversion” (the claim that the Jews are perpetrating a Holocaust in Palestine) exists on the left, surely the true home of Holocaust denial is on the right (as Wistrich notes in passing).

Wistrich himself documents that even within the ranks of the most strident leftists one can still find principled support for Jews and the State of Israel. He cites, among others, Jean-Paul Sartre and Simone de Beauvoir. He quotes from a recent interview with Fidel Castro who asserted that Israel had an unequivocal right to exist, adding that “I don’t think anyone has been slandered more than the Jews. I would say that they have been slandered much more than the Muslims because they are blamed and slandered for everything. No one blames the Muslims for anything.”

You can choose to take a leftist or a rightist worldview, but avoiding antisemitism shouldn’t, on the evidence before us, be the motivating factor for your choice.