There is a depressing inevitability about the way in which what used to be called the eternal verities – the traditions and assumptions on which the specimen life is based – have a habit of crumbling into dust. Last week's instant disintegration involved Her Majesty's Revenue & Customs, a beacon of scrupulousness, one had always thought, keen on impartial judgements and the principle that everyone is equal before the tax-gatherer, but now, at any rate according to the Public Accounts Committee, happy to abase itself before the wealthy and well-advised at the expense – the literal expense – of the ordinary taxpayer.
Set against this exacting yardstick, the idea of Christmas, the reasons for which we celebrate it and the behavioural assumptions that lurk behind it, swiftly descends into a kind of mythological sewing basket, full of differently coloured threads and scraps of cloth, each ripe to be hauled out and reconfigured into a garment of highly questionable authenticity. The average citizen, for example, who imagines that the festive ritual he, or she, is about to participate in is as ancient as the religious texts that lie at its core, is horribly misguided.
The paraphernalia of the modern Christmas – greetings cards, trees, the reverential exchange of presents – is only as old as Queen Victoria: a process of codification undertaken, as the later 19th century wore on, for reasons that were partly spiritual, partly social and – an explanation always worth bearing in mind when public festivals are being discussed – economic.
And if Christmas has, since its early Victorian makeover, been in a constant state of evolution, then its status as an inter-generational marker-flag – a means of comparing present instability and excess to past solidity and sobriety – has never been in doubt. One of the things that used to annoy me about the Christmases of my teenage years was the way in which the older people present always complained about everything. Turkeys, naturally, had lost their savour since the days when they grubbed up worms in the dirt rather than being confined to broiler sheds, and the brandy butter had forfeited its tang.
All this implies that those involved were deploring a collapse in material standards, and yet, as I soon discovered, the lesson the older generation really burned to impart to you was one about frugality and straitened means. In fact, listening to one's grandparents, you sometimes got the impression that the middle-class child of the early 20th century was lucky if its stocking contained a threepenny bit and a medium-sized orange.
At the same time this air of change, and by implication degeneration, was, and is, deceptive. How did the Taylors celebrate Christmas 40 years ago? Well, crib service on Christmas Eve, a second church visit on Christmas morning with my father embarrassing everyone by singing descant lines on top of the carols, grandparents arriving for lunch, the Queen's Speech, and a curious feeling not exactly of saturnalia, but of sumptuary privations being momentarily relaxed, the queer sensation that if you asked for a second, or even a third, helping you could be pretty sure of getting it, while the mountain of crystallised ginger slowly reduced itself to scree and Slade's "Merry Christmas Everybody" blared out from Christmas Top of the Pops.
And how will the Taylors be celebrating in 2013? Well, crib service on Christmas Eve, church again on Christmas morning, blow-out lunch, the Queen's Speech at 3pm... And what exactly is being celebrated? The birth of our Lord, naturally, but half-a-dozen other things whose substance is more or less impossible to convey, that have to do with family, association, consanguinity, and, when it comes down to it, sheer endurance. On each Christmas Day in the 1970s there would come a point at which my father – now, alas, no longer here to warble the descant – would remark to my mother "Well, that's another one we've got through." At the time I used to wonder what he meant. Now, having reached the age he was then, I know precisely.
Another feature of the Christmases of 40 years ago – just as much as those of the 2010s – was the volley of complaints about consumer excess, primed with pious reflections that the "real message of Christmas" had been lost. But these, too, a little historical research insists, are misdirected. The post-Victorian Christmas has always been a materialist orgy. Only the other day I was reading an old J B Priestley novel which describes the Christmas season of what must have been 1929, set in a London full of shops piled to the rafters with boxes of crackers, parcel-festooned shoppers crowding out the buses and party-goers gorging themselves sick.
It is instructive, in this context, to exhume an essay that George Orwell contributed to the left-wing weekly Tribune 67 years ago. Orwell was a man who enjoyed denying himself things, an instinctive puritan who regarded the first stirrings of modern consumer culture with deep misgivings, and yet the line he follows – even when one takes into account six years of rationing – is that of the unrepentant sensualist. Certainly there is a paragraph or two about the "thousand million or so human beings" living in extreme poverty who will be lucky if they get any kind of meal at all on Christmas Day, but essentially Orwell finds the idea of a pared-down, simple-lifer's Christmas to be anathema.
"A deliberately austere Christmas would be an absurdity. The whole point about Christmas is that it is a debauch – as it was probably long before the birth of Christ was arbitrarily fixed at that date." Orwell then goes on to supply what, again, is a very un-Orwellian account of Christmas Day seen from the child's point of view, in which "Christmas is not a day of temperate enjoyment, but of fierce pleasures which they are quite willing to pay for with a certain amount of pain."
Naturally, there are distinctions to be made between 2013 and 1946. For one thing, the three-quarters or so of the nation's children with the good fortune to live above the breadline are quite likely to be so festooned with hi-tech playthings that another batch on Christmas morning rather loses its impact. But the fundamental point remains. It is probable that most people waking up on Christmas morning have only the vaguest notion of what they are celebrating, and no doubt large numbers of Advent calendars are bought by purchasers who have no idea what Advent means.
On the other hand, as Orwell insisted, one celebrates a feast for its own sake, knowing that a detailed inspection of one's motives will turn up a host of paradoxes and inconsistencies that are best not gone into. We have few enough communal rituals. If Christmas inspires even the vestiges of a collective spirit, then its disadvantages – awful television, Boxing Day malaise, the adverts which imply that the ability to buy your nearest and dearest cheap rubbish is a sign of moral salubrity – are a small price to pay.