Is casting out devils a sign of a true Christian?

What follows is one scholar’s way of reading this disagreement — a critical-historical view that often concludes the texts genuinely disagree. It draws on the peer-reviewed sources listed below and stands as one position among the answers above, presented for transparency, not as GEBible’s position.

How critical scholarship weighs this: Usually considered reconciled

This summarizes where critical scholarship tends to land on this tension — a report on the field’s center of gravity, not GEBible’s own ruling.

Two things need stating up front: the lead proof-text is textually secondary, and once the surviving texts are read carefully the supposed three-way contradiction is better described as theological nuance.

Mark 16:9-20, the 'Longer Ending' that supplies the casting-out-demons sign in v. 17, is absent from the two oldest and best Greek uncials, Codex Sinaiticus (ℵ) and Codex Vaticanus (B), both fourth century, and from the Sinaitic Syriac, important Old Latin witnesses (notably Codex Bobbiensis, which has a different 'Shorter Ending'), and a substantial number of Armenian and Georgian manuscripts. Eusebius and Jerome report that the passage was missing from almost all the Greek copies known to them. Its vocabulary and style diverge markedly from authentic Mark, and the syntactic seam at 16:8 (the abrupt *ephobounto gar*) shows that vv. 9-20 were appended to round off a Gospel that early scribes found uncomfortably open-ended (Metzger; Marcus). The critical consensus, reflected in the NA28 apparatus and the bracketing or footnoting of the passage in the NRSV, NIV, and ESV, is that 16:9-20 is a second-century addition. Building a contradiction on Mark 16:17 means building it on a passage that almost certainly was not original to Mark.

The tension survives in attenuated form without that verse, but it reduces to nuance. Mark 9:38-40, paralleled at Luke 9:49-50, has the disciples report *eidomen tina en tō onomati sou ekballonta daimonia* — 'we saw someone casting out demons in your name' — and forbid him *hoti ouk ēkolouthei hēmin* ('because he was not following us'). Jesus answers *mē kōlyete* ('do not stop him') and *hos gar ouk estin kath' hēmōn hyper hēmōn estin* — 'whoever is not against us is for us.' (Notably the Matthean saying at 12:30 runs the other way — 'whoever is not with me is against me' — a separate logion in a different polemical context; the two are not strictly contradictory because their reference points differ.) Exorcism in Jesus's name is here treated as effective and tolerable even by a non-disciple.

Matthew 7:22-23, part of the Sermon on the Mount and without Markan parallel, has many plead *kyrie kyrie, ou tō sō onomati... daimonia exebalomen?* — 'Lord, Lord, did we not... cast out demons in your name?' — only to hear *oudepote egnōn hymas; apochōreite ap' emou hoi ergazomenoi tēn anomian* — 'I never knew you; depart from me, you workers of lawlessness.' The point is not that exorcism is illegitimate but that it cannot by itself authenticate a saving relationship.

The harmonization (Carson; France; Davies-Allison; Hagner) distinguishes the social and theological functions of the act. The narrative of the sons of Sceva (Acts 19:13-16), where Jewish exorcists invoke 'the Jesus whom Paul proclaims' and are overpowered, shows the early church's own awareness that the powerful Name could be wielded — even disastrously — by those outside genuine discipleship. So: outsiders may perform exorcisms (Mark 9); believers characteristically do (Mark 16, if it were authentic); and performing them proves nothing about one's standing before Jesus (Matthew 7). These are three statements about distinct relationships to the act, and they are logically consistent. The question, 'is exorcism a sign of a true Christian,' is answered by the canon with a coherent 'it accompanies them but does not by itself prove them' — not with three incompatible verdicts.

Where the critical reading lands: the lead citation (Mark 16:17) is a textually secondary interpolation and should not anchor the claim; the remaining Mark 9 / Matthew 7 material is nuance, not contradiction, and is harmonizable. The framing overstates the conflict.