In 1756 Voltaire, self-proclaimed defender of liberty, published a virulently antisemitic essay about the Jews. They had, he said, contributed nothing to the civilisation of the world, no art, no science, no philosophy, no original thought even in religion. "In short," he concluded, "we find in them only an ignorant and barbarous people who have long united the most sordid avarice with the most detestable superstition."
Within two centuries after those words were written, Jews had produced a stream of geniuses who transformed the very foundations of Western thought: in physics Einstein, in sociology Durkheim, in anthropology Levi-Strauss, in psychiatry Freud, in politics Marx, in music Mahler and Schoenberg, in literature Proust and Kafka, Bellow and Canetti.
A mere fifth of a per cent of the population of the world, Jews have produced 39 per cent of Nobel Prize winners in economics, 26 per cent in physics, 28 per cent in medicine, nine winners of the Nobel Peace Prize and 47 per cent of world chess champions.
It is an unparalleled achievement, so much so that a former editor of The Times, William Rees-Mogg, wrote that "any modern man who has not learned to think as though he were a Jew can hardly be said to have learned to think at all".
Yet it is an achievement tinged with sadness. Many of these figures either renounced Judaism or, like Marx and Wittgenstein, came from families that had done so. It was inevitable. In 19th-century Europe, there were simply too many doors closed to Jews. Heinrich Heine called baptism his "entrance-ticket to European culture".
Jewish intellectuals in the age of antisemitism were in effect secular marranos. They hid their identity. In some cases - again, Marx and Wittgenstein are examples - they overcompensated by developing attitudes that were themselves antisemitic. They were highly conflicted individuals, and they sought, through their work, to overcome that conflict.
The paradigm case was Spinoza, the first modern Jew. Spinoza, as Yirmiyahu Yovel reminds us, came from a family of marranos, Jews who, under Spanish persecution, publicly embraced Christianity while privately remaining Jews. This left them doubly alienated. They were regarded with suspicion by Christians because they were ethnically Jewish, and with disdain by Jews because they had abandoned their people and faith.
It is not surprising that they or their children said: a plague on both your houses, and sought a world in which there were neither Jews nor Christians, but just people. They placed their faith in the Enlightenment, science and a highly abstract form of reason. Only in such a world could they be free.
There are two kinds of atheist. There are those who simply don't believe in God. But there are others who, with an almost religious fervour, seek to create a world in which there is no religion at all. Of the second kind, a disproportionate number have been Jews or ex-Jews, most notably Marx, Freud, and Spinoza himself. Only in a world purged of religion could people be free to be not this or that - but simply to be.
It didn't happen. The tragedy, whose depth is still not fully appreciated, is that, with the exception of Britain, the very countries that gave birth to the Enlightenment were also those that gave birth to racial antisemitism, and eventually the Holocaust. Nor can this be written off as a nationalist reaction against the Enlightenment, or a revolt of the xenophobic masses against a tolerant elite.
The truth is that, for more than two centuries, many of Europe's greatest minds, especially its philosophers, were also deeply antisemitic.
They include Kant, Fichte, Hegel, Schopenhauer, Nietzsche and Frege. The greatest German philosopher of the 20th century, Martin Heidegger, was an enthusiastic member of the Nazi party, which he joined not when Hitler came to power, but four years earlier in 1929. Not once, after the War, did he express remorse.
The Enlightenment was not accidentally antisemitic, but essentially and fundamentally so. It valued the universal; it despised the particular. But in 19th-century Europe, Jews were the very embodiment of particularity. Their religion was different; so were their customs, culture, their very way of thinking. The more Jews tried to be like everyone else, the more different they appeared, because if you really are like everyone else, you don't have to try.
As the late Reb Shlomo Carlebach used to say, "If someone says, I'm just a human being, I know he's a Jew."
That chapter in European intellectual history is now closed. For me, the image that captures its almost unbearable pathos is of Sigmund Freud in 1939, exiled from Vienna where his people were about to be turned into ashes, frantically writing his last work, Moses and Monotheism, in which he tried to show that Moses wasn't Jewish. By then it was too late to do anything but weep.
The intellectual challenge facing Jewry today is quite different. It is to think and write as Jews. We have earned the right to do so, and in the wake of the failure of the Enlightenment we have a duty to do so. A world in which to gain a hearing you have to pretend to be other than you are is intellectually and morally untenable.
Rather than reject our heritage, we must now give it its full ethical and spiritual dignity. For Judaism really is unique.
It is a supreme example of a religion predicated on education, scholarship and the life of the mind. Study, said the sages, is higher even than prayer. The seats of honour in the synagogue were reserved not for the rich or powerful but for the learned. Paul Johnson described rabbinic Judaism as an "ancient and highly efficient social machine for the production of intellectuals".
Judaism is the only religion in which human beings - Abraham, Moses, Jeremiah, Job - argue with God Himself. Socrates was sentenced to death by the citizens of Athens for doing what every Jewish parent regards it as his or her duty to do: teach the young to ask questions. Which other civilisation could have coined the phrase "argument for the sake of heaven"?
The point goes deeper. Judaism is unique in having a dual structure that honours both the universal human condition and the particularity of systems of meaning.
That duality runs through the whole of Judaism. The Torah begins with humanity as such: Adam and Eve, Cain and Abel, Noah and the Flood, Babel and its builders. Only then does it turn its attention to one family, Abraham, Sarah and their children, and the singularity of their mission and faith.
It embodies a dual covenant. God makes one with Noah and through him with everyone. He then makes a far more specific and demanding covenant with Abraham and later with the Israelites at Sinai, calling on them to become "a kingdom of priests and a holy nation", and create a society built on justice and compassion.
Judaism recognises two kinds of knowledge. One is Torah, the other, chochmah, "wisdom".
The first is unique to Jews. The second is the heritage of humanity as such. The sages said this explicitly: "If you are told there is wisdom among the nations, believe it. If you are told there is Torah among the nations, don't believe it."
Torah is the truth we inherit, wisdom is the truth we discover. Torah is what our ancestors received at Sinai and handed on in an unbroken tradition to successive generations.
Wisdom is what human beings have discovered for themselves by observation and inference. Most of the books of Tanach are dedicated to Torah, but not all. There are entire works that focus on wisdom, most famously Kohelet (Ecclesiastes), Mishlei (Proverbs) and Job.
So high was the sages' regard for "secular" wisdom that they coined a special blessing to be said on seeing an eminent non-Jewish scholar. They praised Greek astronomy. Maimonides wrote books on logic and medicine. He said that the natural sciences and philosophy are paths to the love and fear of God.
In Judaism, "secular" wisdom - the sciences and humanities - is not secular at all. It has religious dignity. It helps us see the universe as God's work and the human person as God's image. The God of revelation, we believe, is also the God of creation. The God who speaks to us through Torah is the God whose wisdom we discover through quantum physics and the structure of the genome.
Judaism is a supreme example of a religion true to its own principles yet open to the wisdom of the world. That is now our intellectual challenge, to think and speak not as secular marranos but as Jews.
There are already wonderful examples. I think of psychotherapists like Viktor Frankl, Aaron Beck and Martin Seligman, who have explored, in different ways, the psychology of hope. Michael Walzer and the late Daniel Elazar have pioneered in developing a Jewish political theory.
Leon Kass, who chaired the President's Council on Bioethics under George W Bush, is also the author of a fine commentary on Genesis. Robert Winston has brought a Judaic sensibility to the treatment of infertility.
When I asked Jeffrey Sachs, the world's leading developmental economist, why he did what he did, he answered without hesitation: Tikkun olam. I have tried in my own work to bring philosophy, sociology, games theory and global ethics into dialogue with Torah.
For 200 years, Jewish intellectuals felt the need to distance themselves from Judaism. That is true no longer. The time is right for a deep, far- reaching conversation between the worlds of Torah and chochmah, the yeshivah and the university, Judaism and the arts and sciences, to create a new generation of religious intellectuals, scholars and poets, who influence the world by engaging with the world.
Not since the golden age of Spanish Jewry have we had such an opportunity to create philosophers like Maimonides, poets like Judah Halevi and statesmen like Abrabanel. The time has come to restore the Judaic voice to the conversation of humankind.