History is Full of Bad Advice

History wasn’t stupid. It was confident. There’s a crucial difference, and it’s the reason so much historical advice reads less like ignorance and more like a man in a very good suit telling you, with total sincerity, that the earth is flat and also here’s a great tip on posture.

Take Galen, the second-century physician whose medical theories dominated Western medicine for more than a thousand years—an astonishing, almost heroic run of being wrong. Galen’s medicine understood health in terms of the balance of the body’s four humours, a theory that helped support centuries of treatments including bloodletting. Here’s the annoying part: Galen was also a genuinely important physician and anatomist whose observations advanced medicine enormously. He wasn’t a crank. He was a brilliant man working inside an elegant, internally consistent, fundamentally wrong system—and generations of doctors kept working inside it.

This is the pattern you’ll see again and again: bad advice rarely comes from stupidity. It comes from someone who reasoned very carefully from the wrong starting point and then interpreted whatever happened next through the same framework, because apparently questioning the framework is for cowards.

Or consider Benjamin Franklin, who was sufficiently devoted to fresh air that John Adams recorded arguing with him over an open bedroom window in 1776. Franklin insisted that the stale air inside their tiny room was worse than the night air Adams feared, then proceeded to explain his theory of colds until Adams fell asleep. The irritating thing is that ventilation genuinely can reduce the transmission of airborne disease, although Franklin didn’t have germ theory available to explain why. Sometimes you can start with the wrong explanation and still stumble into useful advice, like a man who wins the lottery by picking numbers based on his cat’s birthday.

Then there’s the nineteenth century’s real triumph of certainty: physicians who argued that too much education could damage women’s health because the developing body had only so much energy to go around. In 1873, former Harvard physician Edward H. Clarke published Sex in Education; or, A Fair Chance for the Girls, arguing that girls who devoted too much of their bodily ‘force’ to study risked damaging either their reproductive systems or their brains.

This was not some anonymous pamphlet handed out by a lunatic on a street corner. This was a Harvard physician making a physiological argument against educating girls in the same way as boys, with the same tone of unimpeachable authority you’d expect from someone explaining gravity.

But here’s what makes this genuinely fun rather than just a highlight reel of past idiots: buried in the same eras, the same medical traditions, sometimes alongside ideas we now know were spectacularly wrong, is advice that was dead right. Ancient Physicians recommended vinegar preparations for cleaning sores and ulcerations. They also used willow for pain and fever, millennia before anyone identified the salicylates responsible or had the faintest idea how they worked.

Nobody involved knew why it worked. They just kept doing it because it seemed to work, which is either the beginning of science or a very lucky coincidence repeated for a very long time.

That’s the real lesson here, and it’s less comforting than “people used to be dumb.” Good advice and terrible advice have historically been delivered with exactly the same ingredient: total, unwavering confidence, often by someone with credentials, in a tone that discourages follow-up questions. Bloodletting and willow bark could both arrive wearing the authority of medicine. One of them just happened to help.

Which raises an uncomfortable question for anyone smugly reading this in 2026: what are we currently doing with total confidence that future people will find both completely reasonable-sounding and completely insane?

History suggests we will not see it coming, because nobody ever does.

That’s sort of the whole trick of bad advice—it never announces itself.

It just sounds like Wednesday.

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