The date of this Oration is probably the spring of a.d. 369.  It is placed by S. Jerome first among S. Gregory’s Orations.  Cæsarius, the Saint’s younger brother, was born probably about a.d. 330.  Educated in his early years at home, he studied later in the schools of Alexandria, where he attained great proficiency in mathematics, astronomy, and, especially, in medicine.  On his return from Alexandria, he was offered by the Emperor Constantius, in response to a public petition, an honourable and lucrative post at Byzantium, but was prevailed upon by Gregory to return with him to Nazianzus.  After a while he went back to Byzantium, and, on the accession of Julian, was pressed to retain his appointment at court, and did so, in spite of Gregory’s reproaches, until Julian, who had long been trying to win him from Christianity, at last invited him to a public discussion.  Cæsarius, in spite of the specious arguments of the Emperor, gained the day, but, having now distinctly declared himself a Christian, could no longer remain at court.  On the death of Julian, he was esteemed and promoted by successive Emperors, until he received from Valens the office of treasurer of Bithynia.  The exact character of this office and its rank are still undecided by historical writers, some of whom attribute to him other offices not mentioned by S. Gregory, which most probably were filled by a namesake.  On the 11th of October a.d. 368 the city of Nicæa was almost entirely destroyed by an earthquake and Cæsarius miraculously escaped with his life.  Impressed by his escape, he received Holy Baptism, and formed plans for retiring from office and (as it seems) devoting himself to a life of ascetic discipline, which were dissipated by his early and sudden death.