Not since Shakespeare declared that something was rotten in the state of Denmark have the inhabitants of that fair country been so disgruntled. A Copenhagen University academic has just produced some research that has shaken every Dane to his irreducible Viking core. He analysed all the products in an Ikea catalogue according to name. What he found was startling. It seems that Sweden's all-conquering furniture firm quite shamelessly names its fanciest futons, tables and chairs after Swedish, Finnish or Norwegian places, while reserving Danish place names for doormats, draught-excluders and cheap carpets.

Min gud, as they say in Danish. That has set the kat among the pigeons. The Danish press has accused Ikea of “symbolically portraying Denmark as the doormat of Sweden”. Ikea's response is that the Danes “appear to underestimate the importance of floor-coverings”. I can't work out whether that retort is a genuine attempt to smoothe ruffled feathers, or yet another sly Swedish dig at their neighbours. Either way, it hasn't helped to mollify the seething Danes.

But could anything do that, at this late stage in their centuries-old rivalry? It was the editor of the Danish paper that exposed this “Swedish imperialist scandal” who put his finger on what is surely the real reason for Danish disquiet. It's a national inferiority complex, pure and simple. “The Swedes,” he explained, doubtless through gritted teeth, “are so perfect at everything.”

That chimes with a conversation I once had with a Danish friend, whom I accused of being jealous to the point of paranoia about the Swedes. “Jealous?” he yelled, his eyes bulging. “What, just because their cars are faster, their lifestyle better, their scenery prettier, their economy stronger, their pop stars glitzier and their blondes sexier? Why should that make me jealous?”

I love a good feud. Quite apart from its value as a source of creative impetus (the world's stock of novels, plays, films and operas would be lamentably depleted if human beings didn't feud) I honestly think that it brings people together. Just consider the English and the French. Because of our intense mutual antipathy we spend far more time obsessing about each other than we would if we got on tolerably well - like, say, the English and the Portuguese. After all, to do a good hatchet-job on someone else's taste in clothes, food and politics - let alone a scornful debunking of their military record stretching back to the 13th century - you have to know them pretty well.

Indeed, some of the most ferocious feuds, fought out week after week in the pages of organs such as The Times Literary Supplement, are between academics working in such esoteric fields that their detested rivals are the only people on the planet who have any notion of what the argument is all about. Or between highly intelligent but narrowly-focused people working in semi-closed communities such as Oxbridge colleges or cathedral chapters - inward-looking establishments in which a single perceived slight can be magnified into a grudge that festers for years and poisons all contact between the parties. As Byron said: “Men love in haste but detest at leisure.”

But the feuds that fascinate me most are those that have absolutely no rhyme or reason behind them - the ones that mirror Tom Brown's famous old rhyme:

I do not love thee, Doctor Fell,

The reason why I cannot tell;

But this I know, and know full well,

I do not love thee, Doctor Fell.

The trouble with the feud between the Swedes and the Danes is that (as with the Americans and the Canadians, or the English and the Scots) the antipathy is too obviously fuelled by a perception that one side has historically used its greater muscle to lord it over the other. Similarly, there's no mystery as to why the MacDonalds hate the Campbells, or the Poles hate the Germans.

A truly gripping feud, by contrast, must have no discernible cause. Or, if it does have one, the cause must be buried so far back in time that nobody can remember what it was. Or it must be so irrelevant to either side's present-day needs as to be hilariously redundant. Remember Jorge Luis Borges's description of Britain and Argentina going to war over the Falklands? “Two bald men arguing over a comb.”

A feud that can be explained is a feud that can be stopped - and that is usually the last thing that anyone involved wants. An irrational loathing of the other side has become an integral part of what identifies them as individuals, tribes or nations. One definition of being Greek is that you don't like Turks. A major function of being a Spurs supporter is to detest Arsenal. A unifying force of Gordon Brown's inner circle - perhaps the only one - is a loathing of Blair.

Nevertheless, it seems to me that even these supposedly unexplainable feuds usually boil down to something that has been replayed and relabelled hundreds of times - but remains basically the same clash of ideologies. Think Sparta v Athens; Roundheads v Cavaliers; or, in modern Britain, “tough” Northerners v “soft” Southerners. It's the eternal conflict between those who work terribly hard, often in adverse circumstances, yet who always end up in the underdog role; and those who appear to glide effortlessly along, yet still manage to acquire a lion's share of the good things in life.

I sense that something of this underlies the current spat between the Danes and the Swedes. Perhaps the Danes are irritated that the Swedes should have achieved such apparently effortless superiority in so many fields when the two nations have such similar histories, roots and languages. But you probably have to be part of this eternal feud to say for certain. Are there any Danes out there who can shed more light? Or are you too busy burying your hatchets ... in the nearest Ikea futon?

A millionaire? How common

The most devalued word in the language? It has to be millionaire. Closely followed by billionaire. There are now so many! Even my children will be millionaires. I'm not boasting, merely being realistic. If they manage to buy a broom cupboard masquerading as a bijou studio flat in London some time in their lives, its value will certainly be more than a million quid before they die. As for billionaires, Britain alone has 49 of them, according to the new Forbes list. Common as muck!

Clearly we need to redefine the word millionaire so that - as when Cole Porter wrote his now rather baffling Who Wants to Be a Millionaire? - it once again denotes riches beyond imagination. I suggest that we apply the term only to people who could spend a million pounds every day and not even notice. My maths is famously dodgy, but I reckon you'd need a lump sum of £3 billion to make enough interest to enter that exclusive club. The likes of Warren Buffett, Bill Gates, the Queen and the Duke of Westminster would easily qualify as “new millionaires”, whereas Sir Richard Branson (worth a mere £2.2 billion) wouldn't. Oh dear. How deliciously humiliating for him!

Strenuous sinning

Good to see that the Church has updated its list of seven deadly sins. But am I the only one to feel that the new lot make rather strenuous intellectual demands? “You offend God not only by stealing, blaspheming or coveting your neighbour's wife,” says the Vatican's spokes-bishop, “but also by ruining the environment, carrying out morally debatable scientific experiments, and allowing genetic manipulations which alter DNA or compromise embryos.”

Gosh. Sounds like an awful lot of hard work in a laboratory, just to have a bit of sinful fun. Think I'll stick to gluttony, sloth - and a spot of lust, if I should be so lucky.