David Aronovitch, a noted journalist  believed that he was the ultimate rationalist, and had written  an important book debunking conspiracy theories...and saw himself as being the great sane man.... until he was in hospital, and  had psychosis in which  he experienced auditory, and visual "hallucinations"..... which were just as real as reality itself.......................................
 
 
http://www.bbc.co.uk/news/health-15881720