We learn from chap. 20, below, that this epistle to Domitius and Didymus was one of Dionysius’ regular festal epistles (for there is no ground for assuming that a different epistle is referred to in that chapter). Domitius and Didymus are otherwise unknown personages. Eusebius evidently (as we can see both from this chapter and from chapter 20) supposes this epistle to refer to the persecution, of which Dionysius has been speaking in that portion of his epistle to Germanus quoted in this chapter; namely, to the persecution of Valerian. But he is clearly mistaken in this supposition; for, as we can see from a comparison of §22, below, with Bk. VI. chap. 40, §6 sq., Dionysius is referring in this epistle to the same persecution to which he referred in that chapter; namely, to the persecution of Decius. But the present epistle was written (as we learn from §23) while this same persecution was still going on, and, therefore, some years before the time of Valerian’s persecution, and before the writing of the epistle to Germanus (see Bk. VI. chap. 40, note 2), with which Eusebius here associates it. Cf. Valesius’ note ad locum and Dittrich’s Dionysius der Grosse, p. 40 sq.