The procurator Festus thought Paul's madness was caused by his great learning, whereas others might have blamed a devil as in the case of Jesus

Frontispiece, Anatomy of Melancholy, Robert Burton, 1638

And as he thus spake for himself, Festus said with a loud voice, Paul, thou art beside thyself; much learning doth make thee mad. But he said, I am not mad, most noble Festus; but speak forth the words of truth and soberness.

 -- Acts 26:24f.

There was a division therefore again among the Jews for these sayings. And many of them said, He hath a devil, and is mad; why hear ye him?

-- John 10:19f.