'At the core of these attempts to stratify sensation was the implicit assertion that pain was a physical phenomenon, expressive of the relation between peripheral nerves and the brain. Through most of the 20th century, Western medical scientists laboured under the misconception that the experience of pain could be pegged to a scale of intensity.'

https://aeon.co/essays/pain-is-not-the-purview-of-medics-what-can-historians-tell-us