I’m reading Druin Burch’s Taking the Medicine, from which I discovered the following anecdote and insight:
In 1757, an English clergyman named Edward Stone took a walk. For unknown reasons (even to Stone) he decided to taste the bark of a willow tree. It was bitter. But it reminded Stone of cinchona, which at the time was used to cure malaria. Stone subscribed to the ancient and erroneous maxim that “many natural maladies carry their cures along with them or that their remedies lie not far from their causes.” From this, he reasoned that “since malaria was very coming in the marshy places where willow grew” Burch writes, “it was likely that the tree would cure the disease.”
Stone collected the bark, waited a few months until it was dry and pounded it into a powder. He began treating patients who had malaria and discovered that the bark was an efficacious treatment. Given that cinchona was expensive (it had to be shipped from South American) this was good news. Stone wrote a letter to the Royal Society and his remedy was adapted around the country.
The problem was the dried willow bark didn’t cure malaria – it simply reduced fevers (it was later synthesized and is now the main ingredient in aspirin). As Burch points it, “Stone’s achievement was to note a real effect of the bark – its ability to bring down fevers – even though he mistook this for a guarantee of its helping provide a cure.” It gets worse. When the Napoleonic war broke out, importing cinchona became harder, which rose the demand for the bark. “Willow, which did not cure malaria, thus partly replaced cinchona, which did.”
So let us term this The Willow Bark Fallacy: improving something based on erroneous beliefs and falsely believing that you know what you’ve improved, which actually renders things worse off in the long run.