There was a time when disruptive women could be burned as witches. The practice seems odd now and even at the time it was controversial; Emperor Charlemagne and most (but not all) contemporary popes condemned it. Even so, burnings persisted, despite a lack of any scientific evidence.
Before you dismiss the stupidity, consider the organic food industry. Millions of people eat overpriced inferior food despite no science supporting the practice.
Witch-burning at least was a distraction from hunger.
Those around the pyre would have been hungry because the crop had failed, the apples were rotten or blight had wiped out the potatoes.
The Green Revolution brought modern agricultural techniques, including fertiliser and pesticides, to the Third World. Through intensive agriculture, obesity is now a greater problem than malnutrition.
But what of those pesticides, growth hormones and chemicals that produce fat cows, juicy apples and straight bananas? Surely there must be some health advantage to eating blighted fruit and gamey goat meat if it means we are not ingesting these toxins?
Probably not. A comprehensive review of the scientific literature last year by Stanford University found no health benefits from organic food.
It did find eating organic food resulted in lower levels of some chemical residues, including in the urine of children, but this was medically insignificant.
"There isn't much difference between organic and conventional foods if you're an adult and making a decision based solely on your health," said Dr Dena Bravata, the review's senior author.
The industry is cautious about making health claims. The chairman of Organics Aotearoa, Brendan Hoare, says organics are about "total health", including the sustainability of the environment.
"Good nutrition is about good soil," he advised me.
He believes organics lead to healthy soil but he does not say eating organic food as opposed to conventionally grown food will make you healthier.
There is evidence that organic practices can be dangerous.
Toxoplasma gondii is a parasite usually transmitted to humans from the family cat, but organic pork has also been shown to have a high incidence of this pathogen. Although not fatal to healthy adults, it can wreak havoc on the very young, the old and the pregnant.
Other risks lurk in the hedgerow. Organic farming is a return to 18th century agriculture and, like 18th century dentistry, it has risks. There are worse things than pesticide. Pests, specifically.
In New Zealand, the organic industry is about $350 million a year and growing annually by 25 per cent, according to an industry-commissioned study last year. And good on them. It is a perfect way for struggling farmers to differentiate themselves in a commodity business.
Organic farming, like homoeopathy, crystals and Methodism, is a quixotic, harmless pastime. Indulge if you want, but understand what it claims and what it doesn't.