Mark 9:16

And he asked them, What question ye with them? And one of the multitude answered him, Teacher. I brought unto thee my son, who hath a dumb spirit; and wheresoever it taketh him, it dasheth him down: and he foameth, and grindeth his teeth, and pineth away: and I spake to thy disciples that they should cast it out; and they were not able.

The nature of the malady which afflicted this child seems to have been compound. The symptoms certainly suggest epilepsy; but the Greek word which describes it is literally "moonstruck" and much more reasonably bears the translation "lunatic." (Both the Emphatic Diaglott and the Nestle Greek text concur in this). Further, there is the phenomenon of demon possession, confirmed by our Savior's conversation with the Twelve afterward. The complicated nature of the malady, as well as the evident slackening of the apostles' faith, perhaps due to the campaign of the scribes, seems to have entered into the failure of the disciples to effect a cure. See under Mark 9:29.