Crossway has a post by John MacArthur and Richard Mayhue that’s adapted from “Biblical Doctrine: A Systematic Summary of Bible Truth”:
Are Demons in the World Today?
Why do demons sometimes receive so much attention from the media? Are the reports biblically correct, or are they just the musings of uninformed people who see a demon behind every bush and under every rock? Has demon activity accelerated in the world? How can one know which concepts are biblically accurate and which are not?
This subject deserves a full-length book, but it will only be summarized here. Consider several preliminary, general observations:
- We affirm the historical reality of Satan and demons, both in the past and in the present, as verified by the Bible.
- We affirm that the Bible admonishes Christians to expect Satan and demons to operate now much as they did in both Old Testament and New Testament times (1 Pet. 5:6–11).
- We affirm that the Bible teaches that, in living out the Christian life, one will experience real spiritual battle with Satan and his army of demons.
- We affirm that Scripture alone, independent of personal experience or clinical data, will truthfully determine the reality of demonic experiences and provide an understanding of encounters with Satan and demons.
- We affirm that instructions in the New Testament Epistles on how to conduct spiritual warfare were not limited to the first century (Eph. 6:10–20).