There were different types of healing in antiquity, some more or less inspired by different levels of scholarly discussions in different medical schools, some more or less oriented around the model of a charismatic healer without scholary knowledge. In Pagan, Jewish and Christian texts which are discribing processes of healing a lot of reasons for diseases and healing are given. This paper will deal with the function of demons in such texts and propose answers to the following questions: In which way pagan and Jewish concepts were transformed in Christian texts? How these concepts of demons 'function' in different types of texts to explain reasons for diseases and healing? How different types of knowledge are hierarchically ordered?