You don’t have to know a lot about history to know that people used to think illness could be caused by too much blood, and so the way to cure illness was to bleed the patient. I heard that George Washington died as a result of being bled to treat pneumonia (turns out it was actually “acute epiglottitis“). We just shake our heads and sigh at the ignorance.
You may not realize that the idea of “having too much blood” made perfect sense, supported by evidence and observation.
(Note: a lot of the following is speculation. While I found historical resources to back up this speculation, the idea of the four humors is so old and runs throughout so many different civilizations, it’s impossible to track down the origin of the idea.)
If you’re eating, you might want to read this later. We’ll wait.
OK, ready to plow ahead?
- Phlegm. People noticed that when you have a cold or numerous other diseases, you have an excess of phlegm. How do you get rid of it? Not much. Just thin it out to make its exit easier, since it naturally comes out the nose. When you do that, you feel better soon. So the excess “must” be the cause.
- Yellow bile. When the ancients referred to yellow bile, they were probably talking about what we might politely call stomach contents. The ancients observed that if you feel nauseated, and then throw up, you feel better. Obviously, the yellow bile causes the problem. How do you get rid of too much? Just get out of the way. Too much “yellow bile” comes out the mouth.
- Black bile. Since we’re gotten started thinking about exits, you’re probably ahead of me on this one. Abdominal pain and cramps, followed by diarrhea, followed by feeling better–obviously too much black bile. (You can probably figure out from this what “black bile” means.) How do you get rid of too much? We really don’t want to talk about that too much, but we all know where it comes out. That brings us to
- Blood. Of the four basic bodily fluids, this is the one that didn’t have a natural place to exit the body. It’s also the only one that didn’t have obvious associations with other symptoms, such as sore throat/stuffy nose, nausea, abdominal cramps, etc. Got a fever, and no other symptoms? By process of elimination (no pun intended), that’s probably a blood problem. So if we’re going to get well, and an exit doesn’t exist, then obviously we need to make one.
It all makes sense when you think about it that way, doesn’t it?
But we’re smarter than that, aren’t we?
We may know now that disease isn’t tied to bodily fluids in this way. We understand, for instance, that rather than being the cause of a cold, having too much phlegm is simply an effect of a virus or bacteria.
However, we still fall prey to a common logical fallacy, called “Cum Hoc, Ergo Propter Hoc,” which means, “With this, therefore because of this.”
For example, it’s easy to show via a chart that as a child’s shoe size increases, his writing abilities also increase. Hardly anyone would assume the shoe size increase caused the improvement in writing (or that the improvement in writing caused the shoe size increase, either). Correlation doesn’t prove causation. But many speakers (and especially politicians) argue that correlation is causation, and most of their audiences are unaware enough of logical fallacies to be fooled by such arguments.
Establishing causation in complex interactions such as social situations, economics, or even medicine is very, very difficult, but there are lots of correlations. In one instance, doctors observed that women taking combined hormone replacement therapy had a lower incidence of heart disease, leading to a recommendation to take HRT to ward off heart disease. But later studies showed HRT could actually cause a slight increase in heart disease. They finally figured out that women who take HRT are more likely to be more affluent, so they get better diets and more exercise.
Lesson for speakers? Be careful of your claims. It will help your credibility when you only claim correlation unless you can find a ton of evidence for causation. And don’t just depend on common sense. After all, common sense is what led to bleeding Washington. (And a lack of common sense leads to Washington bleeding us, but that’s another post.)
Experience only goes so far. Observation only goes so far. Your own reasoning only goes so far. Be a skeptic, even of your own thinking. (Note: skeptics simply test everything; it doesn’t mean doubt everything.)
P.S. Remember, the next time you slam your thumb in the door, you may be able to shout “black bile” even in polite company.