Intrusion and internalisation of the devil: popular saints vs. the Fathers of the Church

In early Christianity, and in the domain of Byzantium in particular, the devil's interference with man took two distinct forms which may be identified as "intrusion" and "internalisation". The intruding form of the devil was presented in the hagiographies of popular saints, while the internalisation form was presented and elaborated upon by the Fathers of the Church. Intrusion was the most striking and characteristic demonic interference with man. It was an invasion of the body by demons or impure spirits that took possession of the person and caused madness and other illnesses. The internalisation form of demonic interference was more subtle and sinister, and although it was not causing mental illness it was affecting the minds of people by inflaming passions and interfering with judgement, thus leading to erroneous actions, contrary to the commands of God. The two forms of demonic interference that were compatible one with the other and might coexist, emerged from the power of the devil. Intrusion was probably more appealing to and understood by the crowds of the peasants addressed by the popular saints while internalisation was better understood by the educated and the town people addressed by the Fathers of the Church. The two forms of demonic interference have had a lasting effect on religious and spiritual thought and practice till modern times.