C. Manifestations in the Human Body
Some eighty references to demons are found in the New Testament.
Demon-possession may manifest itself as a mental illness accompanied by violence (Matthew 8:28; Acts 19:13-16). It may cause dumbness (Matthew 9:32,33) or blindness or both (Matthew 12:22), or bodily infirmity (Luke 13:11,16). Insanity, lunacy, epilepsy, blindness, dumbness, fevers, aches and pains frequently accompanied demon-possession but they are not necessarily identified with it.
Several New Testament passages indicate that the demons recognised the Messiah, became disturbed at His presence and feared lest He destroy them (Mark 1:34; 9:20, 26; Luke 4:34, etc.). It appears that they could speak, though it may be unclear whether it was the demon or the person himself who was speaking.
In general, it should be added that the New Testament narrators are unconcerned about theoretical discussions on the nature of demons and their activities. They do not indulge in sensationalism and grotesque description. Obsession with or even interest in demons as such is absent. More than on the demons these narratives focus on the victims of demons and Jesus as the healer. They form an integral part of the Gospel and its proclamation that in Jesus the Messiah the Kingdom of God has come into this world.