The word demon does not mean today what it meant in the past. In the past, demons were simply spirits. They were not good or evil by nature. Demons have become misunderstood creatures. While there is evil in both the seen and unseen world, the term “demon” has become a generic catchall for everything evil.
“If our personality survives, then it is strictly logical or scientific to assume that it retains memory, intellect, other faculties, and knowledge that we acquire on this Earth. Therefore ... if we can evolve an instrument so delicate as to be affected by our personality as it survives in the next life, such an instrument, when made available, ought to record something.” Thomas Edison
