This important letter was written a.d. 360, when Basil, shocked at the discovery that Dianius, the bishop who had baptized him, had subscribed the Arian creed of Ariminum, as revised at Nike (Theod., Hist. Ecc. II. xvi.), left Cæsarea, and withdrew to his friend Gregory at Nazianzus.  The Benedictine note considers the traditional title an error, and concludes the letter to have been really addressed to the monks of the Cœnobium over which Basil had presided.  But it may have been written to monks in or near Cæsarea, so that title and sense will agree.