Albert Barnes on Acts 18:12

And when Gallio. After the Romans had conquered Greece, they reduced it to two provinces, Macedonia and Achaia, which were each governed by a proconsul. Gallio was the brother of the celebrated philosopher Seneca, and was made proconsul of Achaia, A.D. 53. His proper name was Marcus Annaeus Novatus; but having been adopted into the family of Gallio, a rhetorician, he took his name. He is described by ancient writers as having been of a remarkably mild and amiable disposition. His brother Seneca (Pref. Quest. Natu. 4) describes him as being of the most lovely temper: "No mortal," says he, "was ever so mild to any one, as he was to all; and in him there was such a natural power of goodness, that there was no semblance of art or dissimulation."

Was the deputy. See this word explained in Acts 13:7. It means, here, proconsul.

Of Achaia. This word, in its largest sense, comprehended the whole of Greece. Achaia Proper, however, was a province of which Corinth was the capital. It embraced that part of Greece lying between Thessaly and the southern part of the Peloponnesus.

The Jews made insurrection. Excited a tumult, as they had in Philippi, Antioch, etc.

And brought him to the judgment seat. The tribunal of Gallio; probably intending to arraign him as a disturber of the peace.

(a) "judgment seat" Jas 2:6