Parapsychologists such as Nandor Fodor and William Roll wrote that poltergeist activity can be explained by psychokinesis.[15][16]
Poltergeist activity has often been believed to be the work of malicious spirits. According to Allan Kardec, the founder of Spiritism, poltergeists are manifestations of disembodied spirits of low level, belonging to the sixth class of the third order. They are believed to be closely associated with the elements (fire, air, water, earth).[17]