“evil spirits” have no influence on human beings – “holy souls have great influence and intense effect”

You have asked regarding the influence of evil spirits. Evil spirits are deprived of Eternal Life. How, then, can they exercise any influence?  But as Eternal Life is ordained for holy spirits, therefore their influence exists in all the divine worlds

…the holy souls have great influence and intense effect, and their influence and continuity do not depend upon physical existence and elemental composition. 

- ‘Abdu’l-Baha  (From a Tablet to Ella Goodall Cooper; Star of the West, vol. 2, no. 15, December 12, 1911) 

(To read the entire Tablet please visit Tablets of ‘Abdu’l-Baha in Star of the West)

Soul and the world of vision

When the souls leave the bodies they do not assume elemental bodies. Whatever man thinks regarding this is but his own imagination.

When man desires help and communication from holy souls, he puts himself in a condition of self-unconsciousness and becomes submerged in a sea of meditation; then a spiritual state, which is sanctified from matter and all material things, becomes visible and apparent to him. Then he thinks he beholds a form. Its appearance is like unto a vision.

Man beholds in the world of vision various images, communicates with them and receives benefits, and in that world of vision he thinks they are physical temples and material bodies, while they are purely immaterial.

Briefly, the reality of the soul is sanctified and purified above matter and material things, but, like unto the world of vision, it manifests itself in these material forms and visages. Likewise in the psychic condition, one beholds the spirits like unto the physical forms and visages. 

- ‘Abdu’l-Baha  (From a Tablet to Ella Goodall Cooper; Star of the West, vol. 2, no. 15, December 12, 1911)
(To read the entire Tablet please visit Tablets of 'Abdu'l-Baha in Star of the West)