There are three kinds of knowledge: true knowledge, no knowledge, and false knowledge.
False knowledge is the most dangerous of the three. It gives assurance about things, and we start acting on extremes. Ancient doctors were sure that bloodletting was good for patients. But it was the opposite. It required two thousand years of mistakes to start questioning the practice, and another one hundred years for the doubts to eliminate the practice. Habits die hard, bad habits kill.
These bad habits have their own categories: unintentional delusions and fallacies by design. The latter again deserves more attention. Take one example. The invention of witchcraft by the Church was a tool for eliminating political opponents. Witches appeared pagan competitors, mostly unchecked by official religious authorities, who, in turn, had close connections with political leaders. Joan of Arc happened to be just the most famous victim of this political tool.
Meanwhile, in the medieval society witches served as doctors, more liberal than Church officials. One of the most brutal attacks on their practices occurred in the 15th century. After the Black Death had killed about half of European population, feudal lords sought ways of increasing their rents. Since the lords had their own fallacies about economic wealth coming from the quantity of workers around, they needed to increase birth rates.
And here, as historian John Riddle suggests, witches became an obstacle. You see, they were pro-choice and helped women with abortions and contraception. Feudal leaders couldn’t like the idea of families making independent decisions about the number of children. Still, you can’t attack the entire population that wants fewer children. What you can do is to destroy professionals who knew how to control births.
Witches did remain miles away from what are now clinical trials. But the Church did worse: it declared their practices illegal saying that some of them actually work. Clergy couldn’t just say that witches had skills people needed and elites didn’t want. Clergy had to invent the image of a dangerous woman with spells and black magic. That was false knowledge about demons on one side and angels on another: neither existed, but the illusion kept living thanks to the strong political support.
Carefully designed fallacies bear hundreds of years of attacks and still persist. They are protected because they are important. And overcoming these fallacies is decisive for human survival. It’s easy to see what false knowledge persists now and how it threatens humans. Say, one relates to the average temperature on the globe. It’s far from being clear how to dissolve this false knowledge.