Richard Thaler,a Business professor from the University of Chicago, has an interesting question:

I am doing research for a new book and would hope to elicit informed responses to the following question:

The flat earth and geocentric world are examples of wrong scientific beliefs that were held for long periods. Can you name your favorite example and for extra credit why it was believed to be true?

He’s gotten a number of interesting answers, and most are reasonable. Rupert Sheldrake, who is famous for his research into parapsychology, avoids self-serving shots at skepticism and talks about determinism. Lee Smolin resists the temptation to mention string theory.

For my money, it’s hard to beat the Four Humors theory of disease and human personality. According to this theory, which began in the ancient world, human disease and human temperaments were governed by the proportion of four substances in the human body: blood, phlegm, black and yellow bile.

Perhaps the only advantage of being poor in the middle ages was not having to deal with physicians who were trained in the four humors. Dealing with the chants and herbs of the village cunning woman would be bliss compared to being regularly bled by a trained doctor, and just as likely to be effective.

I can’t say why this was persuasive, except that it was probably the first systematic treatment of both disease and personality. It probably appealed to that type of person who wants big theories that explain everything at once. Since the humors could correspond to the four greek elements (fire, earth, air, water) it could be seen as a theory of nearly everything.

I also can’t explain why Tim LaHaye has apparently tried to bring back the four temperaments idea. Except that … it’s Tim LaHaye, and nonsense is what he does.

In James Shapiro’s history of the Shakespeare skeptics, Contested Will: Who Wrote Shakespeare, he mentions in passing a historian and Lutheran minister with the irresistible name of Samuel Mosheim Schmucker. Schmucker was the author of a work entitled Historic Doubts about Shakespeare, which may have been the first published work suggesting that Shakespeare, if he even existed, never wrote the plays attributed to him. It’s strong stuff:

British national pride must needs have some great dramatist to uphold the nation’s honor. For politic reasons Shakespeare was selected as the most suitable person to bear the imposture and the glory. Greatness thus became associated with his name. He became, in the progress of time, and from the influence of confirmed prejudice and ignorance and pride, supreme in the literary world.

This was in 1848, almost a decade before Delia Bacon would elliptically suggest the plays were actually written by Francis Bacon. Schmucker was independently the first, though he never suggested a substitute author.

But what’s this? The subtitle of Schmucker’s book was Illustrating Infidel Objections Against the Bible. Yes, in fact the entire work was a parody, aimed at Higher Criticism in general and David Friedrich Strauss in specific. Schmucker was aghast at how Strauss had taken a scalpel to the New Testament and concluded that the Gospels contained almost no historical content. And so Schmucker tried to turn the same arguments against Shakespeare. Surely no one would suggest that Shakespeare hadn’t really written those plays. Right?

I used to do something similar to Schmucker whenever the topic was the denial of evolution. Whenever someone trotted out the old line about evolution being “just a theory,” I’d shoot back, “just like the germ theory of disease.” It seemed like a good rejoined. After all, who’s going to deny one of the bedrock theories in medical science?

So I was a bit pained to read this otherwise excellent article at Respectful Insolence : Yes, there really are people who don’t accept the germ theory of disease.

Medicine does, however, have its version of a theory of evolution, at least in terms of how well-supported and integrated into the very fabric of medicine it is. That theory is the germ theory of disease, which, as evolution is the organizing principle of biology, functions as the organizing principle of infectious disease in medicine. When I first became interested in skepticism and medical pseudoscience and quackery, I couldn’t envision how anyone could deny the germ theory of disease. It just didn’t compute to me, given how copious the evidence in favor of this particular theory is. It turns out that I was wrong about that, too.

Damn.