Matthew 17:15 - Ellicott's Commentary On The Whole Bible

Lunatick. — See Note on Matthew 4:24. The other Gospels add some further touches. The boy had a “dumb spirit.” When the spirit seized him it “tore him,” and he foamed at the mouth, and gnashed with his teeth. Slowly, and as with difficulty, the paroxysm passed off, and the sufferer was wasting away under the violence of the attacks. The phenomena described are, it need hardly be said, those of epilepsy complicated with insanity, a combination common in all countries, and likely to be aggravated where the “seizure,” which the very word epilepsy implies, was the work of a supernatural power. A prolonged melancholy, an indescribable look of sadness, a sudden falling, and loss of consciousness, with or without convulsions, or passing into a tetanic stiffness, a periodical recurrence coinciding often with the new or full moon (hence probably the description of the boy as “lunatick”), grinding the teeth, foaming at the mouth, are all noted by medical writers as symptoms of the disease. The names by which it was known in the earlier stages of medical science were all indicative of the awe with which men looked on it. It was the “divine,” the “sacred” disease, as being a direct supernatural infliction. The Latin synonym, morbus comitialis, came from the fact that if a seizure of this kind occurred during the comitia, or assemblies of the Roman Republic, it was looked upon as of such evil omen that the meeting was at once broken up, and all business adjourned. Whether there was in this case something more than disease, viz., a distinct possession by a supernatural force, is a question which belongs to the general subject of the “demoniacs” of the Gospel records. (See Note on 8:28.) Here, at any rate, our Lord’s words (Matthew 17:21) assume, even more emphatically than elsewhere, the reality of the possession. (See Mark 9:25.)