John Calvin 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. This outcry that Festus makes shows how little the truth of God prevails with the reprobate: namely, though it is ever so plain and evident, yet it is trodden underfoot by their pride.

For although the things Paul had alleged from the Law and the Prophets had nothing in them resembling madness but were grounded in good reason, Festus attributes them to madness. He does this not because he sees any absurdity, but because he refuses what he does not understand.

Nothing was more foolish or more distasteful than the superstitions of the Gentiles, so that their high priests were, for good reasons, ashamed to speak of their mysteries, whose folly was more than ridiculous.

Festus grants that there was learning packed into Paul’s speech. Nevertheless, because the gospel is hidden from the unbelievers, whose minds Satan has blinded (2 Corinthians 4:3), he thinks Paul is a brain-sick fellow who handles matters intricately.

So, although he cannot mock and openly despise him, Festus is so far from being moved or inwardly touched that he considers Paul a man who is frenzied and of mad curiosity.

This is why Festus cannot bring himself to pay attention to what Paul says, fearing that he too might go mad. In the same way, many today flee from the word of God, lest they drown themselves in a labyrinth.

And they think that we are mad because we raise questions about hidden matters, and so become troublesome both to ourselves and to others.

Therefore, being admonished by this example, let us beg God to show us the light of His doctrine. Let us also ask that He will give us a taste of it, lest through obscurity and difficulty it become distasteful, and at length, this proud disdain erupts into blasphemy.