I have always been hazy as to the precise connection between the Jewish festival of Shavuot and the Christian festival of Pentecost, which often, if not always, occur on the same day - today. I know that it is Shavuot because I read the Jewish Chronicle, having also, in 2004, arranged for Simon Hughes and Charles Kennedy to visit Temple Fortune (that's a North London high street, not a Wild West frontier town) and (as is traditional at Shavuot) eat cheesecake, as part of Simon's London mayoral election campaign. Was Mr Kennedy there? I think he was, but I am not certain, as I was not there myself, being as I was on a freebie foreign trip that it would have been discourteous to say no to. And I know that today is Pentecost because the BBC was earlier broadcasting a live television programme featuring modern hymns of the sort that remind me why I like the older ones so much.

Consulting the Bible (or the BBC website, as it also known), it turns out that Pentecost (http://www.bbc.co.uk/religion/religions/christianity/holydays/pentecost....) began on a day on which the Christian apostles "were celebrating (the Jewish festival of Shavuot (http://www.bbc.co.uk/religion/religions/judaism/holydays/shavuot.shtml)) when the Holy Spirit descended on them. It sounded like a very strong wind, and it looked like tongues of fire. The apostles then found themselves speaking in foreign languages, inspired by the Holy Spirit. People passing by at first thought that they must be drunk, but the apostle Peter told the crowd that the apostles were full of the Holy Spirit."

So the New Testament basically tells us that a bunch of Jews was celebrating Shavuot, when down came the Holy Spirit to meet this bunch of Jews, who then became Christians and stopped celebrating Shavuot and began celebrating Pentecost instead, to commemorate the Shavuot visit of the Holy Spirit, a visit which Christians believe to have marked the birth of the Christian Church.

This is a reminder that the Christian Church was not born with Jesus, but was created by Christians in response to their interpretation of Jesus' teachings. Shavuot is the festival at which Jews commemorate what they believe to be God's giving of his teaching (the Torah) to his people at Mount Sinai. In terms of Christianity's belief that it offers a New Testament - a new covenant - to follow or supersede the covenant entered into by God and his people at Mount Sinai, it is logical that Christians would, to cut a long story short, adapt Shavuot into a new festival (Pentecost), to celebrate their new covenant, just as Shavuot celebrates the Sinai covenant.

Shavuot is itself a pentecost, as a pentecost is simply a counting of fifty days - Jews count fifty days after Pesach (Passover) before celebrating Shavuot, and Christians count fifty days after Easter before celebrating Pentecost.

I am not saying anything remotely original here. This all ought to be basic general knowledge for teenage schoolchildren. It does fascinate me, though, that, thousands of years on from the composition of the New Testament, Christians are still celebrating Pentecost, and Jews are still celebrating the much older festival of Shavuot. Of the British Jews and Christians that celebrate today, I wonder how many are aware that the major Christian festival of Pentecost has its roots in the apostles having celebrated the major Jewish festival of Shavuot? It's the sort of basic thing that both of them (Jews and Christians) should know about each other if we are all to know enough about each other to get along.

I actually have never celebrated Shavuot. I grew up going to the Liberal Jewish Synagogue in St Johns Wood, before stopping going at the age of eleven because I wasn't enjoying it and because I wanted to stay at home and watch television on Saturday mornings. I remember one occasion on which the children carried flowers around the synagogue, which must have been for Shavuot, but apart from that, I've never celebrated it. Entirely arbitrarily and illogically, I grew up going to synagogue on the High Holy Days of Rosh Hashanah and Yom Kippur, and celebrating the festivals of Pesach and Chanukah at home. Other Jewish festivals - Purim, Shavuot, Simchat Torah, Sukkot - were, in my childhood, a closed book.

This means that, on a deeply personal level, I have no emotional connection to those other festivals, the ones that I have never celebrated (although there is a friend that I often go to for dinner during Sukkot, I should say). In particular, as a fairly formal English, German-influenced Jew, I feel no connection to the idea of donning fancy dress and going wild for Purim (http://www.bbc.co.uk/religion/religions/judaism/holydays/purim_1.shtml) - I would never want to don fancy dress and go wild for anything, and such a festival therefore has, for me, nothing to do with religious devotion. A book by the Chief Rabbi makes me think about religion. The language of the King James Bible, or the architecture of St Paul's Cathedral, can remind me of what I like about religion, just as a country pub reminds me of what I like about England. This has nothing to with logic, religious orthodoxy or even common sense - it has to do with emotion, personal experience and an inchoate sense of what seems "normal" to me, based on what I did when I was a child.

I still celebrate Chanukah and Pesach at my parents' home, and I did get into the habit, around ten years ago, of fasting and going to synagogue on Yom Kippur, as the idea of spending a day contemplating what one has got right and wrong in the past year, and thinking about how one might try to do things better in the year ahead, works for me as an idea. I still do that in most years. Actually, this year, I didn't fast as I was on medication, and I was with some friends one of whom wanted to pop in (literally that) to a nearby strictly Orthodox, Lubavich service in Edgware, so we did. You didn't need to be wearing a suit, you didn't need to have booked, you just turned up, explained that you were Jewish, got a polite welcome, and stayed for as short or long a time as you wanted to - ten minutes, in my case. It was taken for granted that one might pop in and out and leave after only a short time, and this was not in any way considered rude or inappropriate. It was all in Hebrew and I wasn't really in the mood, hence my swift departure; I was really only there out of courtesy to one of my friends, who stayed longer than I did, albeit out of my sight behind a curtain, as men and women were, of course, strictly segregated there.

But is it not ironic that these strictly Orthodox Jews simply welcomed me as a Jew, without caring what sort of a Jew I might be? Whereas if I'd gone to some other synagogues that are actually 'less religious' and not strictly Orthodox, then I wonder if I might have been expected to explain where I am coming from Jewishly, in a way that would set my teeth on edge? It is not strictly Orthodox Jews who have ever made me feel uncomfortable about being a non-religious Jew called Matthew whose father is not Jewish. That is because they are secure in their faith, and their faith teaches them that I am a Jew, and that is good enough for them. It is, however, not always good enough for some other, less religious Jews who have, occasionally, left me feeling that they cannot get their head around my family background.

The only other festival that I particularly celebrate is Christmas, having grown up with my Christian grandparents and uncle arriving to visit us on Christmas Eve. We still have an utterly traditional Christmas lunch with a stuffed turkey and bread sauce, after which we watch the Queen on television. I consider this to be part of my heritage, being descended father to son from many generations of rural English Christians. I am an agnostic who was brought up Jewish, with a Jewish mother and an agnostic, non-Jewish father from an Anglican family. So, yes, I am Jewish, read the Jewish Chronicle every week, consider myself a member of the Jewish faith because I was raised Jewish and have never joined another religion.

And yes, I enjoy having enough Jewish literacy to understand an essay by an Orthodox rabbi, and yes, I grew up eating pork and still happily eat it, as I personally have no religious beliefs that tell me not to. If I'm in a pub and there's a beer from Oxfordshire, I'll drink that one, because my paternal grandmother was born in Bodicote. I like going to the Czech restaurant in West Hampstead (http://www.czechoslovak-restaurant.co.uk/) because it serves middle-European food and was once a haunt of central European Jewish refugees including my grandparents. Its entirely unkosher food reminds me of the German food cooked by my German Jewish grandmother. My only moral dilemma about eating the boiled knuckle of pork is that it is arguably too fatty for a man of my increasingly advanced years. And yet I can also whip up an accurate, sourced briefing for anyone in public life who needs to know what Orthodox Jews believe about kosher food, faith schools and who-is-a-Jew, and this, for me, is not paradoxical.

I once went to the Czech restaurant at Christmastime with my grandfather and other elderly Jewish relatives who were in seasonal pursuit of carp and goose, those being traditional Christmas foods in the central European countries in which these people had all been born. One of them was a convinced atheist, at whose funeral (nay, cremation, which Orthodox Jews don't do) was played a piece of Jewish religious music by Ernest Bloch, with the son of the deceased saying that yes, his father had been an atheist, but he'd also been proud to be a Jew, with the music being played so that any religious Jews present could spend a few minutes thinking about their Judaism, at what was otherwise a non-religious service. By the way, my candidate to be the UK's next Chief Rabbi is Michael Friedländer (http://en.m.wikipedia.org/wiki/Michael_Friedl%C3%A4nder), who was a cousin of my great grandfather's. Michael Friedländer has, admittedly, sadly been dead since 1910, but I see no other reason to disqualify him from the post.

This all came up last year when Ed Miliband (who is Jewish, and was born to two Jewish parents, and has never converted to any other religion) married his non-Jewish partner in a non-religious ceremony. Reportedly, Mr Miliband chose to smash a glass as part of the ceremony - smashing a glass being a customary part of a religious Jewish wedding. On at least one blog, comments were posted suggesting that it was ridiculous and pointless for Mr Miliband to have enacted a Jewish custom at a non-Jewish wedding. These people did not understand that a non-religious person like Mr Miliband could feel an emotional, familial connection to a Jewish religious custom. If I ever get married, I will presumably have a non-religious wedding, and I can definitely imagine inviting an Orthodox Jewish friend to recite a Jewish prayer in Hebrew at the reception, to recognise that I am Jewish, as being Jewish is part of who I am, even if I might be marrying someone who is not Jewish. I could say that this is because identity is complicated, but, actually, it's the other way round: identity is very simple, for those of us who are interested in who our different ancestors were. I do not find my identity complicated at all.

Jonathan Freedland wrote well on this in Friday's Jewish Chronicle: http://www.thejc.com/comment-and-debate/columnists/68050/isaac-jacob-mos...