Matthew 17:14

And when they were come to the multitude, there came to him a man, kneeling to him, and saying, Lord have mercy on my son: for he is epileptic, and suffereth grievously; for oft-times he falleth into the fire, and oft-times into the water.

The word "epileptic" as used in the English Revised Version (1885) is an error, as may be seen by consulting any Greek lexicon or commentary. The word is "lunatic." This class of disease was given separate listing in Matthew 4:24, and doubtless many of this kind were healed. In the case here, there is the additional complication of demon possession. The fact that there was a double affliction could have accounted for the difficulty the disciples had in healing the boy, failing, in fact, to do so. (See on Matthew 8:28).