When you have a colonoscopy, you are given a drug called midazolam. Apparently it is an amnesiac, so you can't remember what happened when you were under its effects. This sounds pretty freaky.
I wonder how this drug was discovered? Perhaps someone was experimenting on themselves by self-administering it, and they suddenly found themselves sitting exhausted and stubbly at the lab bench with an empty bottle of midazolam in front on them, wondering what the hell just happened.
The reason I bring it up is that I recently heard talk of a gastroenterologist who, each year, has several patients who refuse to pay him for colonoscopies that he has performed because they don't remember anything happening and thus accuse him of trying to trick them.
It's kind of the inverse problem of Descartes' evil demon, which fed him false sensory data to undermine his ability to obtain any reliable knowledge. If only Descartes had had more colonoscopies - I'd like to hear his perspective.