For the Jews of Europe, these are the best of times and the worst of times. In Britain, in the past 20 years, we have built more Jewish day schools than ever. Culturally, a community deemed moribund a generation ago boasts a cultural centre, a community centre in the making, Jewish Book Weeks, arts, music and film festivals, and an adult education event - Limmud - that has inspired offshoots in 50 other centres throughout the Jewish world.
Both parliamentary speakers, in the Commons and the Lords, are Jewish. We have had, in recent years, two Jewish lord chief justices, Jewish heads of Oxford and Cambridge colleges, a Jewish editor of The Times and Jewish leaders of both the Conservative and Labour parties. Not only are Jews respected, so is Judaism. The Jewish moral voice has become a significant part of the national conversation.
These are astonishing achievements. But they are clouded by the disturbing phenomenon of a new antisemitism spreading like a virus across Europe. This cries out for explanation --- after the Holocaust, if there was one thing on which people of goodwill throughout the world agreed it was: Never again.
Out of the determination that there should never be another Holocaust came the United Nations Declaration of Human Rights, the concept of a "crime against humanity", the idea that racism is a vice, the movement for interfaith dialogue and the historic shift in Christianity known as Vatican II, Nostra Aetate.
How then, did antisemitism return to the very nations that pledged themselves never to repeat it? The cynical answer is that it never died, it merely went underground. But, as a line of reasoning, this is misleading. For the new antisemitism is only secondarily aimed at Jews as individuals. Its real target is Jews as a nation in their national home, Israel.
The Jewish moral voice is a part of the national conversation
For centuries, Europe had been disfigured by crude, theologically driven, Christian anti-Judaism. Jews were accused of poisoning wells, spreading plague, desecrating the host and killing Christian children. Jews were not the only victims of the Church. "Witches" and heretics were burned. Then, after the Reformation, Christians started killing their fellow Christians in Europe's great wars of religion.
That was when thoughtful people said: "Enough" and created the rise of science, the age of reason, the doctrine of toleration and eventually the emancipation of hitherto disenfranchised minorities, including Jews. It was the most enlightened age in European history, and it was at this precise time, in Paris, Berlin and Vienna, the most sophisticated centres of all, that a new form of hate was born - racial antisemitism. As the deadliest virus the West has ever known, it led otherwise ordinary, decent human beings to do, or remain passive witnesses to, unspeakable acts.
The antisemitism of the 19th century was not the crude anti-Judaism of the Church. Similarly, the new antisemitism of the 21st century is not the racist antisemitism of the 19th. It is not directed against individual Jews but against Jews as a nation. It is not spread by conventional means but by the new technologies of communication - websites, e-mail, blogs and social networks - that are almost impossible to monitor and control.
Its most brilliant, demonic, stroke has been to adopt as weapons the very defences created against the old antisemitism. It accuses Israel of the five cardinal post-Holocaust sins: racism, apartheid, crimes against humanity, ethnic cleansing and attempted genocide. It is designed to mislead, and it works. Israelis and American Jews see it as a threat to European Jewry but the real target is Israel - and where Israel is most vulnerable: among the opinion-forming classes of Europe. If Israel is delegitimised in their eyes, that leaves only America, and the shrewd judgment of Israel's enemies is that, when it comes to supporting Israel, America will not go it alone for ever.
This is a long-term and coldly calculated chess-game that aims at the destruction of the Jewish state. To counter it will call for a co-ordinated global Jewish response beyond anything so far envisaged. Nor is it a battle that can be fought and won by Jews alone. Without allies, Jews and Israel will lose.
Antisemitism is always the symptom of something more pervasive, an unresolved tension within a culture, that targets Jews but never stops with them. It was not Jews alone who died at the hands of medieval Christianity, Tsarist Russia, Nazi Germany and Stalinist Russia: it was freedom itself. The same will be true in the 21st century. Those who deny Jews or Israel their freedom will lose, or fail to gain, their own.