σεληνιάζομαι

From the study of Matthew 4:24

Range of meaning

Literally 'to be moon-struck' (from selēnē, 'moon'). It was the popular term for seizure disorders, with sudden falls, convulsions, foaming and rigidity, which people blamed on the moon's influence (BDAG: 'be epileptic').

Against the English

KJV has 'lunatick', following the Vulgate's lunaticos, Latin luna, 'moon'. BSB and NIV have 'those having seizures'. WEB and NASB have 'epileptics'. YLT has 'lunatics'.

How it drifted

English 'lunatic' kept the moon idea but came to mean mental illness, then became an insult. The KJV reader today hears 'madmen', not seizures.

Used elsewhere in the period

Only here and in Matt 17:15, where the boy 'is moonstruck and suffers terribly, often falling into fire and water'. In 17:18 a demon is driven out of him. The Hippocratic treatise On the Sacred Disease (5th–4th century BC) argues against blaming epilepsy on gods. Later writers (e.g. Galen, Aretaeus) note popular links between seizures and the moon. Compare Ps 121:6: 'nor the moon by night'.

From the study of Matthew 17:15

Range of meaning

Built on σελήνη (selēnē, “moon”), it means “to be moonstruck”. In use it describes someone who has recurring fits: sudden collapse, convulsions, loss of consciousness. The word names the symptoms and also hints at what people thought caused them. It does not make a precise diagnosis.

Against the English

KJV and YLT have “lunatic” (from Latin luna, “moon”), which now means “insane”. WEB and ESV have “epileptic” and BSB, NIV and NLT have “has seizures”. These describe the symptoms accurately but drop the moon imagery.

How it drifted

The Vulgate translated it lunaticus. In English “lunatic” moved away from “subject to fits linked to the moon” toward madness in general, so by the modern period the KJV's word suggests a mental illness the Greek does not describe.

Used elsewhere in the period

In the New Testament it appears only in Matthew (4:24 and here). In Matt 4:24 “the moonstruck” are listed separately from “the demonised” and “the paralysed”. The belief that the moon could harm people lies behind Ps 121:6 (“the moon [will not strike you] by night”; LXX Ps 120:6). BDAG cites the verb from astrological writers of the Roman period. The Hippocratic treatise On the Sacred Disease (5th c. BC) already argued against blaming seizures on gods. Origen (Commentary on Matthew 13.6) discusses this verse: physicians explained the condition naturally from the moon, while Origen held that an unclean spirit timed its attacks to the moon's phases.