How do we know bloodletting doesn’t work?

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Author note.

Explore voice = Exploratory style. Very punchy. Personal, and lively using “me,” “you,” “us,” and “I” freely.

I want you to feel me right there with you. We use “I” and “me” and “us” without apology. If the Explain voice is a bridge, the Explore voice is the hike we take across it. It is lively, reflective, and sometimes a bit raw. It is the sound of a shared exploration where I lead you by the hand, but we both discover the view at the same time.

This is where I get to think out loud. Not with definitions, we aren’t just looking at the facts; we are looking at how they feel and what they mean for our lives. I’m talking to you about what I’ve found and what I’m still figuring out. It is engaging because it is real, and it is reflective because it is honest.

The goal is real advice and enjoyable reading. I want to land on something you can actually use. It’s about being direct, being punchy, and making sure that by the time we reach the end of the page, we’ve both found something worth keeping.

And now the piece.

How do we know bloodletting doesn’t work?

This is a great example of the false cause logical fallacy—because for over 4,000 years, bloodletting was widely accepted as a cure for illness. Imagine the shock professional doctors must have felt when, in the 1830s, studies showed that bloodletting didn’t help—it actually harmed patients.

Bloodletting was popular because some patients seemed to get better afterward. But that improvement had nothing to do with blood loss. This was just a false cause fallacy in action: the doctors assumed the treatment caused recovery, but it was really the body healing itself.

Science is a process, not a set of fixed facts. Even after discovering that bloodletting didn’t work, it took decades to persuade doctors, and many clung to the old ways. Change didn’t fully take hold until a new generation of doctors could “hear” the truth and accept evidence over tradition.

So, how do we know bloodletting doesn’t work? We proved it through observation and experimentation—key to avoiding false cause fallacies.

Here's the key idea. Bloodletting survived for millennia not because it worked, but because humans mistook timing for causation.

Finally, the core takeaway. A false cause fallacy assumes that one event directly causes another without proof. It links two events improperly, ignoring other factors, often leading to flawed conclusions based on coincidence, not causality.

That Critical Thinking FAQ,

was first published on TST 2 years ago.

The flashcard inspired by it is this.

Front: What logical fallacy kept bloodletting in use for centuries?

Back: False cause

All this is part of the broader TST project.

Tidbits are written to stand alone, but they are also designed to interlock—forming a research layer that supports deeper synthesis.

The goal is not to persuade quickly, but to build a stable framework where ideas can be tested honestly.

The end!