Lunatic

Lunatic (from Latin luna, the moon) was a term used in the Authorized Version (Matt. 4:24; 17:15) to translate the Greek seleniazetai (moonstruck), reflecting the ancient belief that epilepsy and certain mental disturbances were influenced by the phases of the moon. The word seleniazetai derives from selene (moon), and the condition described in Matthew 17:15—for he is a lunatic and sore vexed, for ofttimes he falleth into the fire and oft into the water—closely describes the symptoms of epilepsy.

Jesus healed this boy immediately after his transfiguration when his disciples had failed to do so. The case is described in detail in all three synoptic Gospels (Matt. 17:14–21; Mark 9:14–29; Luke 9:37–43); Mark's and Luke's accounts identify the condition as caused by an evil spirit. This combination of a disease-like presentation with spiritual causation reflects the New Testament's recognition that some physical afflictions in the Gospel period had demonic origin, without implying that all such conditions do. Jesus rebuked the unclean spirit, and the boy was healed immediately.