Paul, thou art beside thyself - "Thou art mad, Paul!" "Thy great learning hath turned thee into a madman." As we sometimes say, thou art cracked, and thy brain is turned. By the τα πολλα γραμματα it is likely that Festus meant no more than this, that Paul had got such a vast variety of knowledge, that his brain was overcharged with it: for, in this speech, Paul makes no particular show of what we call learning; for he quotes none of their celebrated authors, as he did on other occasions; see Acts 17:28. But he here spoke of spiritual things, of which Festus, as a Roman heathen, could have no conception; and this would lead him to conclude that Paul was actually deranged. This is not an uncommon case with many professing Christianity; who, when a man speaks on experimental religion, on the life of God in the soul of man - of the knowledge of salvation, by the remission of sins - of the witness of the Spirit, etc., etc., things essential to that Christianity by which the soul is saved, are ready to cry out, Thou art mad: he is an enthusiast: that is, a religious madman; one who is not worthy to be regarded; and yet, strange to tell, these very persons who thus cry out are surprised that Festus should have supposed that Paul was beside himself!
Festus said with a loud voice - Amazed at the zeal of Paul. Paul doubtless evinced deep interest in the subject, and great earnestness in the delivery of his defense.
Thou art beside thyself - Thou art deranged; thou art insane. The reasons why Festus thought Paul mad were, probably:
(1) His great earnestness and excitement on the subject.
(2) his laying such stress on the gospel of the despised Jesus of Nazareth, as if it were a matter of infinite moment. Festus despised it; and he regarded it as proof of derangement that so much importance was attached to it.
(3) Festus regarded, probably, the whole story of the vision that Paul said had appeared to him as the effect of an inflamed and excited imagination, and as a proof of delirium. This is not an uncommon charge against those who are Christians, and especially when they evince unusual zeal. Sinners regard them as under the influence of delirium and fanaticism; as terrified by imaginary and superstitious fears; or as misguided by fanatical leaders. Husbands often thus think their wives to be deranged, and parents perceive their children that, and wicked people assume the ministers of the gospel to be crazy. The frivolous think it proof of derangement that others are serious, anxious, and prayerful; the rich, that others are willing to part with their property to do good; the ambitious and worldly, that others are willing to leave their country and home to go among the Gentiles to spend their lives in making known the unsearchable riches of Christ. The really sober and rational part of the world they who fear God and keep his commandments; they who believe that eternity is before them, and who strive to live for it - are thus charged with insanity by those who are really deluded, and who are thus living lives of madness and folly. The tenants of a madhouse often think all others deranged but themselves; but there is no madness so great, no delirium so awful, as to neglect the eternal interest of the soul for the sake of the pleasures and honors which this life can give.
Much learning - It is probable that Festus was acquainted with the fact that Paul was a learned man. Paul had not, while before him, manifested particularly his learning. But Festus, acquainted in some way with the fact that he was well-educated, supposed that his brain had been turned, and that the effect of it was seen by devotion to a fanatical form of religion. The tendency of long-continued and intense application to produce mental derangement is everywhere known.
Doth make thee mad - Impels, drives, or excites thee περιτρέπει peritrepeito madness.