Charles Ellicott Commentary Acts 26:24

"And as he thus made his defense, Festus saith with a loud voice, Paul, thou art mad; thy much learning is turning thee mad." — Acts 26:24 (ASV)

Festus said with a loud voice—The description may be noted as one of the touches of vividness indicating that the writer relates what he had actually heard. The Roman governor forgot the usual dignity of his office, and burst, apparently, into a loud laugh of scorn.

Much learning doth make thee mad—The Greek gives a neuter plural: Your many writings are turning you to madness. The word was one which was used by the Jews for the collected body of their sacred writings and traditions, as in the letters of John 7:15 and the holy Scriptures of 2 Timothy 3:15. Festus had probably heard the Law and the Prophets of Israel so described, and knew that St. Paul had with him books and parchments (2 Timothy 4:13), which he was continually studying.

That one who had been crucified should rise from the dead and give light to the Gentiles seemed to him the very hallucination of insanity. So have people at all times thought of those who lived by a higher law than their own, whether their faith rested, as in St. Paul’s case, on an outward objective fact, or, as in Wisdom 5:4, on a true faith in the Unseen.