LUNATIC (from Greek σεληνιαζόμενος, derived from σελήνη “moon”). — The ancients called lunatics those afflicted with epilepsy (the falling sickness, the sacred disease, the comitial malady), which was attributed to the influence of the moon.
Among the many sick people healed by Jesus near the Sea of Tiberias there were also lunatics (σεληνιαζόμενοι; Mt 14:24), who in this instance are distinguished from the demoniacs (συμμονιζόμενοι).
The lunatic healed by Jesus after the Transfiguration (q.v.), however, was also a demoniac. The event is narrated by all three Synoptics (Mt 17:15, among the symptoms of the illness, writes: σεληνιαζεται; “lunaticus est”; Mk 9:14-29 gives more details; Lk 9:37-43 follows a middle course). That the boy was not only epileptic but also possessed by a demon is clear not only from the impression made upon the father and the Apostles (who may have reflected the common popular belief that attributed such maladies, especially these, to the devil) but also from the explicit statement of the Evangelists and, above all, from Jesus’ exorcism: “Thou dumb and deaf spirit, I command thee, go out of him, and enter not into him any more” (Mk 9:25).
The symptoms of dumbness and deafness and other details are not those of epilepsy. The hypothesis that Jesus accommodated Himself to a popular misconception by speaking thus is untenable: He taught the reality of diabolical possession, and after the miracle He added to the Apostles, who were grieving that they had not been able to cast out the evil spirit, “This kind can come forth by nothing, save by prayer [and fasting]” (Mk 9:29).