The other day I was having a conversation with a Jewish intellectual and the question came up, as it often does, as to the nature of Jewish identity. What are we? What makes us Jewish? This has been one of the persisting debates about Jewish life ever since the nineteenth century. Until then, people, by and large, knew who and what Jews were. They were the heirs of an ancient nation who, in the Sinai desert long ago, made a covenant with God and, with greater or lesser success, tried to live by it ever since. They were God’s people.

Needless to say, this upset others. The Greeks thought they were the superior race. They called non-Greeks “barbarians,” a word intended to resemble the sound made by sheep. The Romans likewise thought themselves better than others, Christians and Muslims both held, in their different ways, that they, not the Jews, were the true chosen of God. The result was many centuries of persecution. So when Jews were given the chance to become citizens of the new secular nation-states of Europe, they seized it with open arms. In many cases, they abandoned their faith and religious practice. But they were still regarded as Jews.

What, though, did this mean? It could not mean that they were a people dedicated to God since many of them no longer believed in God or acted as if they did. So it came to mean a race. Benjamin Disraeli, converted to Christianity by his father as a young child, thought of his identity in those terms. He once wrote, “All is race — there is no other truth,” and said about himself, in response to a taunt by the Irish politician Daniel O’Connell, “Yes, I am a Jew, and when the ancestors of the right honourable gentleman were brutal savages in an unknown island, mine were priests in the temple of Solomon.”

The trouble was that hostility to Jews did not cease despite all that Europe claimed by way of enlightenment, reason, the pursuit of science and emancipation. It could now, though, no longer be defined by religion, since neither Jews nor Europeans used that as the basis of identity. So Jews became hated for their race, and in the 1870s a new word was coined to express this: antisemitism. This was dangerous. So long as Jews were defined by religion, Christians could work to convert them. You can change your religion. But you cannot change your race. Anti-Semites could only work, therefore, for the expulsion or extermination of the Jews.

Ever since the Holocaust, it has become taboo to use the word “race” in polite society in the West. Yet secular Jewish identity persists, and there seems no other way of referring to it. So a new term has come to be used instead: ethnicity, which means roughly what “race” meant in the nineteenth century. The Wikipedia definition of ethnicity is “a category of people who identify with each other based on common ancestral, social, cultural, or national experiences.”

The trouble is that ethnicity is where we came from, not where we are going to. It involves culture and cuisine, a set of memories meaningful to parents but ever less so to their children. In any case, there is no one Jewish ethnicity: there are ethnicities in the plural. That is what makes Sefardi Jews different from their Ashkenazi cousins, and Sefardi Jews from North Africa and the Middle East different from those whose families originally came from Spain and Portugal.

Besides which, what is often thought of as Jewish ethnicity is often not even Jewish in origin. It is a lingering trace of what Jews absorbed from a local non-Jewish culture: Polish dress, Russian music, North African food, and the German-Jewish dialect known as Yiddish along with its Spanish-Jewish counterpart Ladino. Ethnicity is often a set of borrowings thought of as Jewish because their origins have been forgotten.

Judaism is not an ethnicity and Jews are not an ethnic group. Go to the Western Wall in Jerusalem and you will see Jews of every colour and culture under the sun, the Beta Israel from Ethiopia, the Bene Israel from India, Bukharan Jews from central Asia, Iraqi, Berber, Egyptian, Kurdish and Libyan Jews, the Temanim from Yemen, alongside American Jews from Russia, South African Jews from Lithuania, and British Jews from German-speaking Poland.

Their food, music, dress, customs, and conventions are all different. Jewishness is not an ethnicity but a bricolage of multiple ethnicities.

Besides which, ethnicity does not last. If Jews are merely an ethnic group, they will experience the fate of all such groups, which is that they disappear over time. Like the grandchildren of Irish, Polish, German and Norwegian immigrants to America, they merge into the melting pot.

Ethnicity lasts for three generations, for as long as children can remember immigrant grandparents and their distinctive ways. Then it begins to fade, for there is no reason for it not to. If Jews had been no more than an ethnicity, they would have died out long ago, along with the Canaanites, Perizzites, and Jebusites, known only to students of antiquity and has left no mark on the civilization of the West.

So when, in 2000, a British Jewish research institute proposed that Jews in Britain be defined as an ethnic group and not a religious community, it took a non-Jewish journalist, Andrew Marr, to state the obvious: ‘All this is shallow water,’ he wrote, ‘and the further in you wade, the shallower it gets.’ He continued:

The Jews have always had stories for the rest of us. They have had their Bible, one of the great imaginative works of the human spirit. They have been a victim of the worst modernity can do, a mirror for Western madness. Above all they have had the story of their cultural and genetic survival from the Roman Empire to the 2000s, weaving and thriving amid uncomprehending, hostile European tribes.

This story, their post-Bible, their epic of bodies, not words, involved an intense competitive hardening of generations which threw up, in the end, a blaze of individual geniuses in Europe and America. Outside of painting, Morris dancing, and rap music, it’s hard to think of many areas of Western endeavour where Jews haven’t been disproportionately successful.

For non-Jews, who don’t believe in a people being chosen by God, the lesson is that generations of people living on their wits and hard work, outside the more comfortable mainstream certainties, will seed Einsteins and Wittgensteins, Trotskys and Seiffs. Culture matters . . . The Jews really have been different; they have enriched the world and challenged it.

Marr himself is neither Jewish nor a religious believer, but his insight points us in the direction of this week’s parsha, which contains one of the most important sentences in Judaism: “Speak to the whole assembly of Israel and say to them: Be holy because I, the Lord your God, am holy.” Jews were and remain the people summoned to holiness.

What does this mean? Rashi reads it in context. The previous chapter was about forbidden sexual relationships. So is the next chapter. So he understands it as meaning, be careful not to put yourself in the way of temptation to forbidden sex. Ramban reads it more broadly.

The Torah forbids certain activities and permits others. When it says “Be holy” it means, according to Ramban, practice self-restraint even in the domain of the permitted. Don’t be a glutton, even if what you are eating is kosher. Don’t be an alcoholic even if what you are drinking is kosher wine. Don’t be, in his famous phrase, a naval bireshut ha-Torah, “a scoundrel with Torah license.”

These are localised interpretations. They are what the verse means in its immediate context. But it clearly means something larger as well, and the chapter itself tells us what this is. To be holy is to love your neighbour and to love the stranger. It means not stealing, lying, or deceiving others. It means not standing idly by when someone else’s life is in danger. It means not cursing the deaf or putting a stumbling block before the blind, that is, insulting or taking advantage of others even when they are completely unaware of it – because God is not unaware of it.

It means not planting your field with different kinds of seed, not crossbreeding your livestock or wearing clothes made of a forbidden mixture of wool and linen–or as we would put it nowadays, respecting the integrity of the environment.

It means not conforming with whatever happens to be the idolatry of the time – and every age has its idols. It means being honest in business, doing justice, treating your employees well, and sharing your blessings (in those days, parts of the harvest) with others.

It means not hating people, not bearing a grudge or taking revenge. If someone has done you wrong, don’t hate them. Remonstrate with them. Let them know what they have done and how it has hurt you, give them a chance to apologise and make amends, and then forgive them.

Above all, “Be holy” means, “Have the courage to be different.” That is the root meaning of kadosh in Hebrew. It means something distinctive and set apart. “Be holy for I the Lord your God am holy” is one of the most counter-intuitive sentences in the whole of religious literature. How can we be like God? He is infinite, we are finite. He is eternal, we are mortal. He is vaster than the universe, we are a mere speck on its surface. Yet, says the Torah, in one respect we can be.

God is in but not of the world. So we are called on to be in but not of the world. We don’t worship nature. We don’t follow fashion. We don’t behave like everyone else just because everyone else does. We don’t conform. We dance to a different music. We don’t live in the present. We remember our people’s past and help build our people’s future. Not by accident does the word kadosh also have the meaning of marriage, kiddushin, because to marry means to be faithful to one another, as God pledges himself to be faithful to us and we to him, even in the hard times.

To be holy means to bear witness to the presence of God in our, and our people’s, lives. Israel – the Jewish people – is the people who in themselves give testimony to One beyond ourselves.

To be Jewish means to live in the conscious presence of the God we can’t see but can sense as the force within ourselves urging us to be more courageous, just and generous than ourselves. That’s what Judaism’s rituals are about: reminding us of the presence of the Divine.   

Every individual on earth has an ethnicity. But only one people was ever asked collectively to be holy. That, to me, is what it is to be a Jew.

For more from Rabbi Sacks, please visit www.rabbisacks.org