by Dr. John Ankerberg, Dr. John Weldon
Demons are not the spirits of dead men, or of some pre-Adamite race, as some argue, for the spirits of the human dead are not free to roam but are confined and under punishment
(Lk 16:19-31; 2 Pet. 2:9).
Nor are demons merely personifications of evil, or of natural forces, such as the “gods” of nature, as skeptics assume. Nor are demons the superstitious designation for particular natural diseases, such as epilepsy or mental illness, because Scripture clearly distinguishes these disorders from demon possession, although it is possible that both can be present or that demon possession could induce mental illness.
To continue click on the link below:
https://www.jashow.org/wiki/index.php/Demons:_What_Are_They