How do we know bloodletting doesn’t work?

By Michael Alan Prestwood

Author and Natural Philosopher

10 Oct 2024

Published 1 year ago.

Updated 1 month ago.

Speed: 1.00

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.

Here is 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 1 year ago.

By the way, 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 make it possible to build slowly and honestly, without losing track of where an idea came from.

Rather than publishing for immediacy, the TouchstoneTruth project releases one edition per week of the TST Weekly Column while allowing ideas to mature long before and long after publication.

The end!