Many times the believer's mind is full of thoughts, and he finds himself unable to stop these thoughts. His mind (head) is like a thinking machine, which has been "turned on" by an external force, thinking continually and uncontrollably. Even though a believer shakes his head incessantly and tries to reject such thoughts, he is not able to do so. The tide of thoughts comes like a rolling wave and refuses to stop day and night. Most believers do not know the reason for this. Little do they realize that this is the work of evil spirits. A believer should know what is "a thought." A thought is his mind grasping a matter. But in an unstoppable train of thought, it is no longer the mind grasping a matter, but a matter grasping the mind! Originally it was the mind thinking about things. Now the mind is not thinking about things, but things are compelling the mind. Many times a believer wants to drop a matter, but an external force seems to remind him in his mind all the time. It does not allow him to forget and forces him to keep on thinking. This is the work of evil spirits.

In short, a believer should investigate all abnormal phenomena. Unless they are due to natural illnesses, all abnormal phenomena are from evil spirits. God does not interfere with the functions of man's natural faculties. God never interjects His thoughts suddenly into man's thoughts, and He never cuts off the work of man's mind suddenly or robs him of anything. All sudden stoppages of thoughts that feel like the brain has become void, sudden appearances of incoherent thoughts in the mind, sudden lapses of memory in the middle of thoughts that feel like a snap of electric wire, or a continual inability to exercise the mind or memory are the result of the works of evil spirits. Because evil spirits have occupied the faculty of the mind, they can seize it at times and stop its functions, or they can relax it at other times and make it active again. A believer should realize that natural causes can produce only natural illnesses. Sudden thoughts and sudden forgetfulness are beyond the control of our will and beyond the course of natural events. For this reason, they must be from some supernatural source. If a believer examines all the phenomena of his mind this way, he will not be ignorant of the reasons for his symptoms.

The book of Ephesians tells us that evil spirits operate "in the sons of disobedience" (2:2). This is a very important matter. Evil spirits work not only outside of man but also inside of man. If we want someone to work, at most we use words and expressions and other body movements. But evil spirits can do more than these. They are able to work not only from the outside, as from one man to another man, but they are able to operate within man. This means that they are able to penetrate into man's mind and work within him, causing man to obey them. Man cannot penetrate into the mind of another man and stealthily suggest many things in private to him, nor can man cause another man to be confused about the source of these suggestions. But evil spirits can do these things. They have ways that are unavailable to man in his normal communication with one another. First they work in man's mind and then reach man's emotion because the mind and the emotion are closely connected. They also begin from the mind and work their way into man's will because the mind and the will are also closely connected.

The way they move is by stealthily and secretly putting their favorite thoughts into man's mind in order to accomplish their goal. Or they may prevent man from thinking anything that they do not want him to think about. The Bible clearly teaches that the authority of darkness can give thoughts to man as well as steal thoughts away from man. John 13:2 says, "The devil having already put into the heart of Judas Iscariot, the son of Simon, that he should betray Him." This speaks of the way Satan puts his thoughts into man's mind. Luke 8:12 says, "Then the devil comes and takes away the word from their heart." This speaks of how Satan takes away the word which man should remember so that man forgets everything. These two verses tell us of the two kinds of work that evil spirits perform in man's mind. By these verses, we can identify the works of the evil spirits. Their works are always to add or subtract something from the mind of man.