Origen De Principiis by Origen
(5) Practical Works.
Under this head we place the little treatise Peri Euches, On Prayer, written at the instance of his friend Ambrose, and which contains an exposition of the Lord's Prayer; the Logos protreptikos eis marturion, Exhortation to Martyrdom, composed at the outbreak of the persecution by Maximian, when his friends Ambrose and Protoctetus were imprisoned. Of his numerous letters only two have come down entire, viz., that which was addressed to Julius Africanus, who had questioned the genuineness of the history of Susanna in the apocryphal additions to the book of Daniel, and that to Gregory Thaumaturgus on the use of Greek philosophy in the explanation of Scripture, although, from the brevity of the latter, it is questionable whether it is more than a fragment of the original. The Philokalia, Philocalia, was a compilation from the writings of Origen, intended to explain the difficult passages of Scripture, and executed by Basil the Great and Gregory of Nazianzum; large extracts of which have been preserved, especially of that part which was taken from the treatise against Celsus. The remains were first printed at Paris in 1618, and again at Cambridge in 1676, in the reprint of Spencer's edition of the Contra Celsum. In the Benedictine edition, and in Migne's reprint, the various portions are quoted in footnotes under the respective passages of Origen's writings.