Sentence:  Believing that an evil spirit is trying to <WSD>obsess</WSD> one is a dangerous belief, and when one comes to believe he is <WSD>obsessed</WSD> by an evil spirit, though there is not an evil spirit within a thousand miles of him, he will have all the symptoms. 
Meaning of the word marked with <WSD> tags:  Influenced or controlled by evil spirits, but less than possessed in that the spirits do not actually reside in the victim.