“A delusion is a belief held with strong conviction despite superior evidence to the contrary.”
“The psychiatrist and philosopher Karl Jaspers was the first to define the three main criteria for a belief to be considered delusional in his 1913 book General Psychopathology. These criteria are:
Certainty (held with absolute conviction)
Incorrigibility (not changeable by compelling counterargument or proof to the contrary)
Impossibility or falsity of content (implausible, bizarre or patently untrue)
Furthermore, when a false belief involves a value judgment, it is only considered a delusion if it is so extreme that it cannot be, or never can be proven true.”
— https://en.wikipedia.org/wiki/Delusion