Leeches are not an important part of a doctor’s pharmacopoeia today.

Imagine that debate between a medieval doctor and a modern Westerner:

Doctor: “Leeches are an important way to correct an imbalance in bodily humors. For example, they can cure pneumonia.”

Modern: “How do you know?”

“This comes from Galen! Anyway, I had pneumonia myself last winter, and I took a treatment of leeches. Look at me now.”

“How do you know the leeches were a part of the cure? Maybe you would’ve gotten over it yourself. Maybe the leeches hurt you, and you got well in spite of them.”

You can imagine how this would continue. The doctor would defend his tradition; he would cite other anecdotes of supposed cures; he might explain the theory of the four humors in Hippocratic medicine; he might say that that’s just how they do things here, and you should keep your nose out of it; he might say that leeches only push things in the right direction, not that they’re a guaranteed cure; he might demand that you prove that leeches are useless or harmful; and so on.

Before you shake your head at the shallowness of thought of our medieval ancestors, at least they had an excuse. Modern science didn’t exist and so hadn’t demonstrated the benefits of hypothesis testing and evidence following. It’s more puzzling when you compare this with a discussion you could have with a Christian today.

Christian: “God answers prayers.”

Skeptic: “How do you know?”

“It’s in the Bible! Anyway, I was jobless for months last year, and my finances were getting desperate, but then I prayed about it. I had a great job in two weeks.”

“How do you know that God was involved? If it was God, why did it take two weeks—shouldn’t you have heard the phone ringing with the job offer right after you said ‘Amen’? Maybe it was all the work you put into the job search that finally paid off.”

You can imagine how this would continue. The Christian would defend their tradition; they would give anecdotes of answered prayer; they might explain how and why prayer works; they might say that that’s just how they do things here, and you should keep your nose out of it; they might say that God has his own perfect way of doing things, not that prayer always works as you’d want it to; they might demand that you prove that prayers aren’t answered or that God doesn’t exist; and so on.

Unfortunately, prayer is just the start of it. You can have similar medieval conversations today about God’s hand in current political events or natural disasters, about God protecting you from covid or protecting the earth from climate change, about God steering Christians’ lives or standing with them during hardship, about the Bible being so remarkable that only divine inspiration explains it, and so on. While these claims are usually stated with confidence, they’re never backed up by convincing evidence.

Evidence didn’t matter much to the medieval doctor, but you’d think that it would be important to a Christian today, living in 21st century society and with a modern education. The problem is that we’re the same superstitious humans with imperfect brains that we were a thousand years ago. And if we’ve been indoctrinated as children, our adult intellect is usually focused on defending our stance, not questioning it.

In a time before modern science, religion answered questions, but only because it was the only option. It exists today, not because it provides useful answers (it doesn’t—its answers are culturally specific and depend on which religion is answering) but because of inertia. Religion has outlived its usefulness.

Here is a thought experiment . . .
tell your wife
that you have a lot of invisible qualities
that can be clearly seen
and see what kind of response you get.
— commenter Otto

(This is an update of a post that originally appeared 5/17/17.)

Image from jimmy brown (license CC BY 2.0)