True-believer syndrome is an informal or rhetorical term coined by M. Lamar Keene in his 1976 book The Psychic Mafia.
He began using the term to refer to people who continued to believe in a paranormal phenomenon or event, even after it had successfully been debunked or proven to have been staged.
In an article published in Skeptical Inquirer, psychologist Matthew J. Sharps and his colleagues analyze and dissect the psychology of True Believers and their behavior after the predicted apocalypse fails to happen.
[12][13] Camping, who was then president of the Family Radio Christian network, claimed the Bible as his source and said May 21 would be the date of the Rapture and the day of judgment "beyond the shadow of a doubt".
On May 23, Camping amended that May 21 had been a "spiritual" day of judgment, and that the physical Rapture would occur on October 21, 2011, simultaneously with the destruction of the universe by God.