I'm not certain, but, in the case of my family member, their "certainty" is that everyone is conspiring to kill them. As I am one of the "conspirators," I can assure you that they are dead wrong.

Also, in my days of yute, I was fairly profligate in the use of ... mind-enhancing chemicals, shall we say. They basically gave me the same exact certainty and "insight."

Once, I decided to write down the marvelous insight that I experienced, while tripping. I wrote a whole bunch of stuff in a notebook, and then read it, a couple of days later.

It was pure gibberish. Made no sense at all.