It seems that Vincent suggests that there was some group of priests that adopted the Arian creed during the Arian persecution of Catholics, that is, they simply accepted the creed presented at the Council of Sirmium in 357 under the auspices of Emperor Constantius II. By priests, he most probably means both presbyters and bishops; compare with the passage: omnes clerici leuitae et sacerdotes ["all clerics, levites, and priests"] in Commonitory XXIV.