I’ll eat almost anything for art: roast guinea-pig in Peru, defrosted cockroaches in California, 35 dishes at a sitting at a gourmands’ club in Copenhagen, the ominously-named olla podrida at home, and, among Chile’s Mapuche, five kinds of slime that are reputed indigenous delicacies. All appetites, however, have limits, imposed not so much by taste as by fear. Sometimes scruples of taste assume fearsome dimensions.

As Christmas approaches I anticipate with horror the one common fowl I will not willingly eat: turkey’s odour makes me think of unwashed linen, and (except in fancy breeds and out of fine kitchens) the consistency of the breast meat, which resembles woollen socks, has a confirmatory effect.

My aversion is not wholly crazy, though it may be eccentric, because it arises from experience. But what about the foods we fear so much that we will not even try them — the forbidden fruits excluded by the most inhibiting of superstitions: the taboo?

With food taboos, there’s no point in asking what the point is. The point is that there is no point

Most food taboos, like most prohibited degrees of incest, are products of culture. If you are English, you jib at horsemeat, or, if a high-caste Hindu, at that of a cow, not because there is any moral or nutritional difference between the two sources of protein, or because of any objective superiority of taste, but because you have grown up with your fellows. I like barbecued pig’s ribs, marinaded in bourbon, but do not invite Muslims to share them.

We all have what I call personal taboos — peculiar to ourselves, unlearned from any school or sodality, yet maintained with the intense, irrational zeal of religious laws.

I recoil from the meat of carnivorous land-animals. My inconsistency is glaring, because I’ll happily eat fish-eating fish. A big lobster, putatively glutted with the flesh of human castaways and suicides, as well as with all the detritus of the sea, makes me slaver greedily. But offer me dog and I’ll politely decline, not because some of my best friends are dogs: I know people who’ll cheerfully kill for the pot chickens they call affectionately by name in the farmyard; and I’ll not fancy a roast fox or a boiled wolf or a fricassee of lion, despite numbering none of their brood among my acquaintance.

Nor do I see anything wrong in principle with flesh-eaters’ flesh. By eating meat myself, I don’t disqualify my carcass from providing a cannibal feast, or from exposure, like a Zoroastrian sacrifice, to the ravages of the ravens, or from nourishing the worms. On the contrary, after an ill-spent life, I find comfort in the thought that, once I am decently dead, I can at last make some beneficial provision for feeding a fellow-creature. My distaste for cooked carnivores has no objective justification: it is purely, even proudly, and entirely irrational.

That is what makes it a taboo. No people can match the BlaTokwa of Botswana for the bizarre variety of their prohibitions. Apart from aardvark —forbidden to everyone — each food has its appointed limits at different times of life for different sections of the community. Adult males may not eat placenta. Honey and tortoise are proscribed for children. The elderly may eat every body part of their favoured meat-source, except the nose.

Lactating women are allowed donkeys’ milk but not eggs. Anthropologists who ask, “Why?” get deservedly silly answers: it’s to protect unborn babies, perpetuate health, or prevent drought. Cicero sought to explain barbarians’ self-denying food ordinances as conservation strategies. Medieval theologians tried to account for Muslim pork-aversion by suggesting that Muhammad’s body had been fed to pigs. Maimonides justified similar Jewish fastidiousness on the grounds that pigmeat was too “moist” to be healthy.

Eat horse and you cease, in your entrails, to be English

The brilliant scholar Mary Douglas thought she had solved the longstanding mystery of the Levitican purity rules when she noticed that prohibited animals were anomalous in the categories that ancient Hebrew taxonomy postulated — but even some of the anomalies are anomalous.

With food taboos, there’s no point in asking what the point is. The point is that there is no point. If there were —  if hygiene or morals or conservation or common interest were served — everyone would adopt the same rules, and the taboo would no longer identify the tribe. To create solidarity, a custom must be peculiar to the group it bonds. Identity is in the bowels. Eat horse and you cease, in your entrails, to be English. Chomp on a cloven-hoofed non-ruminant and you become an outcast among ancient Hebrews.

The same considerations apply, mutatis mutandis, to personal revulsions so strong that we fear to break them. Irrationally pollutant foods imperil the integrity of the person, just as they menace the unity of the tribe. If I eat turkey it makes me feel sick. If I were to eat cat or fox, I should feel changed. The fear that makes us fastidious is fear of ceasing to be ourselves.