an evil spirit: a real, personal, malevolent being that works under Satan and is driven out by Jesus
This is the meaning the word carries almost everywhere in the New Testament. A demon is not a vague force or a figure of speech but a personal being that opposes God, harms people, and answers to a chief named Satan or Beelzebul. In the Gospels the word is used interchangeably with "unclean spirit" and "evil spirit," so the same being can be called all three within a single story.
The one core runs through every shade below. A demon can seize and torment a person, and Jesus casts it out; it can be the real power that people unknowingly bind themselves to when they worship idols; it can be hurled as an insult at someone thought to be mad or in league with evil; it can be a being that knows perfectly well who God is and trembles; and it can be the hidden source behind teaching that leads people astray. In each case the demon is treated as actual, organized, and hostile.
The New Testament is reserved about where demons came from. It is sure they are real, personal, malevolent, and already defeated by Christ, but it never spells out an origin (fallen angels, the spirits of dead giants, demoted foreign gods). That silence is deliberate, and readers should resist filling it in with a single tidy explanation that the text itself does not give.
Nuances
Disputed
What the New Testament writers thought demons fundamentally are, since the text never states an origin for them.
- contestedThe New Testament gives no settled doctrine on the question; the later Christian package that fuses fallen angels, demoted pagan gods, and the spirits of dead giants into one category is a second and third century development read back into the text.; Dale Martin, "When Did Angels Become Demons?" JBL 129 (2010); Annette Yoshiko Reed, "When did Daimones become Demons?" HTR 116 (2023)
- contestedDemons are demoted gods of the nations, the dominant Jewish framework still operating in the New Testament, especially where Paul cites the Song of Moses.; Emma Wasserman, Apocalypse as Holy War (Yale, 2018); Paula Fredriksen, Paul: The Pagans' Apostle (Yale, 2017)
- contestedDemons are the disembodied spirits of the dead giants of Genesis 6, the dominant Second Temple explanation of evil-spirit affliction.; Loren Stuckenbruck, The Myth of Rebellious Angels (Mohr Siebeck, 2014); Archie T. Wright, The Origin of Evil Spirits (Mohr Siebeck, 2005)
- contestedThe traditional Christian view, that demons are fallen angels under Satan, is already implicit in the New Testament.; Clinton Arnold, Powers of Darkness (IVP, 1992); Sydney Page, Powers of Evil (Baker, 1995)