The Bible teaches a threefold demonology: 'unclean spirits,' 'familiar spirits,' and 'seducing spirits' are three distinct categories of evil spirit, each requiring different handling.

"Unclean spirit" (Greek pneuma akatharton) is Gospel-and-Acts vocabulary, showing up in exorcism accounts across Matthew, Mark, Luke, and Acts, with a single similar phrase back in Zechariah 13:2. The Gospel writers themselves use "unclean spirit," "evil spirit," and "demon" interchangeably within the same stories: Mark will call the same being an unclean spirit in one verse and a demon in the next. That alone shows it isn't marking off a special category; it's one of several overlapping ways the Gospels describe the affliction Jesus casts out.

"Familiar spirit" is something else entirely. It's the King James rendering of the Hebrew ob, an Old Testament term tied to necromancy, most famously the medium of Endor whom Saul consulted in 1 Samuel 28. "Familiar" here doesn't mean "well-known," the way it sounds to modern ears. The translators (following the earlier Geneva Bible) borrowed the Latin familiaris, a household servant or intimate of the family, to describe a spirit supposedly bound to a medium the way an attendant is bound to a household. It's a sixteenth-century English word doing a job that sense of the word no longer does in modern English.

"Seducing spirits" appears exactly once, in 1 Timothy 4:1, and the underlying Greek word (planos) doesn't carry a romantic sense of seduction at all; it means "wandering" or "leading astray," the same image used elsewhere for a lost sheep. Paul is warning about false teaching and doctrinal apostasy in the last days, not describing an exorcism or a necromancy ritual. Set the three side by side and they don't touch: one is Gospel exorcism language, one is Old Testament necromancy language carrying a centuries-old English translation choice, and one is Pauline language about false teachers. Every word is genuinely in the Bible. The "three types of spirits" system that treats them as one unified taxonomy (implying three different categories each needing its own deliverance method) is something readers built on top of three separate words that were never meant to sit on the same shelf.