Schizophrenia or Personality Disorder?

Joan's Mental Dispositions

• The voices she heard from "God" were considered Schizophrenic auditory hallucinations she assumed as God's voice. 
• The voices she heard cannot be attributed to Schizophrenia as she is not recorded to have manifested any other symptom of Schizophrenia. 
• She is recorded to have lead a behaviorally normal life as any manifestation of psychological symptoms such as impaired motor coordination, paranoia, thought disorder, compulsive behaviour etc. would be seen as madness
• The 'mad' or those with mental disorders were executed
• Thus, her voices cannot be attributed to schizophrenia
• Alternate explanation-Hers was a personality disposition that allowed her to perceive thoughts from her own conscience, and attribute them to the voice of God

Source:(Dr. Miguel Farias from the Department of Experimental Psychology, Oxford University) National Geographic Mystery files: Joan of Arc