Demonology is discussed in theological colleges only in the most general way. There just is not time to study the subject with any degree of thoroughness. Consequently there is much vagueness and at time error in the Protestant pulpit when Satan and the demons are mentioned. Nothing of any importance has been written on the subject, from a Reformed standpoint, since John L. Nevius, a Presbyterian missionary in China, wrote his Demon Possession and Allied Themes in 1894. There has been a steady trickle of Dispensationalist writing on the subject and in recent years a number of books by evangelical authors have appeared. They are mostly superficial in their treatment of the subject. Some of them contain wild and unwarranted statements and a few of them are positively dangerous for the unwary to read. Publishers have sensed a market for such books and in a day when we hear much about extrasensory perception, ouija boards, black witches, exorcism and suchlike, there has been a tendency to rush out books on the occult, sprits and demon-possession which pay scant attention to the Biblical evidence, pander to the sensational and often arrive at unwarranted conclusions.

There is a crying need for an examination of this whole subject in the light of Scripture alone, bearing in mind that the Scriptures are our only rule of faith and practice. We are concerned to confess what has been revealed in Scripture and not what is partly the result of logical deduction and subjective opinion. All available details and reports relating to the phenomena of Satanic activity and demon-possession are to be studied, but they must be interpreted in the light of Scripture and not used to form a basis for conclusions or to colour the interpretation of Scripture

Frederick S. Leahy, Satan Cast Out (Edinburgh: The Banner of Truth Trust, 2017), 7-8.