True believer

From SkepticWiki

"The true believer syndrome merits study by science. What is it that compels a person, past all reason, to believe the unbelievable. How can an otherwise sane individual become so enamored of a fantasy, an imposture, that even after it's exposed in the bright light of day he still clings to it--indeed, clings to it all the harder?" -- M. Lamar Keene True Believer Syndrome