Cæsarius was the youngest brother of Gregory of Nazianzus.  After a life of distinguished service under Julian, Valens, and Valentinian, he was led, shortly after the escape narrated in this letter, to retire from the world.  A work entitled Πύστεις, or Quæstiones (sive Dialogi) de Rebus Divinus, attributed to him, is of doubtful genuineness.  Vide D.C.B. s.v.  The earthquake, from the effects of which Cæsarius was preserved, took place on the tenth of October, 368.  cf. Greg. Naz, Orat. x.