DIDIMO il CIECO. — Ancient ecclesiastical writer, born around 313 in Alexandria, where he spent his entire life, and died there between 395 and 399. He became blind at the age of four; nevertheless, he succeeded in acquiring an extremely extensive education, especially in sacred subjects, to such an extent that he was placed at the head of the Didaskaleion, the Alexandrian catechetical school. During his long period of teaching, he counted Rufino and s. Girolamo among his disciples. He remained a layman, but devoted himself to an ascetic life and imbued his doctrinal activity with profound piety.
His works, so numerous that s. Girolamo (De vir. ill., 109) declined to list them, are exegetical and dogmatic. Of the Old Testament, he commented at least on the Psalms, Job, Isaiah, Hosea, Zechariah, and Proverbs; of the New Testament, on the Gospels of s. Matteo and s. Giovanni, the Acts of the Apostles, the First Epistle to the Corinthians, and those to the Galatians and Ephesians; only scant remains of them survive in the biblical Catenae. The attribution to D. of an Enar ratio in epistolas canonicas, mentioned by Cassiodoro (Inst. div. litt., 8) and transmitted to us in the Latin version of Epifanio Scolastico, encounters difficulties. In exegesis D. follows Origene, concerning himself with the establishment of the critical text,
but above all indulging in a pronounced allegorism. Of his dogmatic works, there survive the De Spiritu Sancto, anterior to 381, in the Latin version of s. Girolamo; the De Trinitate, in three books, written between 381 and 392; and, mutilated, the short treatise Contra Manicheeon. Some of his writings must have come down to us under another name: among these is the πρῶτος λόγος (first discourse), which D. mentions in the De Trinitate and which, probably identical with the De dogmatibus et contra Arianos attested by s. Girolamo, would be preserved in Books II, IV, and V of the Contra Eunomium, falsely attributed to s. Basilio, who authored the first three books. The Ps.-Atanasio’s Contra Macedonianos diol. would likewise be a work of D. But the attribution to D. of the Ps.-Girolamo on Is. 6:1–7 (L. G. Morin, Anecdota Mareësoana, III, III, p. 1030), proposed by W. Dietsch (Didymus V. Alexandria als Verfasser der Schrift über die Seraphen - Vision, Fribourg 1942), has not gone unchallenged. Other dogmatic works are lost.
D.’s Trinitarian doctrine, fully in conformity with the Nicene faith, is inspired by s. Atanasio and the Cappadocians. As with Basilio, his formula is: μία οὐσία, τρεῖς ὑποστάσεις (one essence, three persons); the Son is consubstantial (ἐμυούσιος) with the Father, and so is the Holy Spirit with the Father and the Son. The three Persons have a single will and operation. The Son comes from the Father through generation, the Spirit through procession (ἐκπρόφυσις). His admiration for Origene, whom he undertook to defend, led him to hazardous and erroneous theories on other points, such as the pre-existence of souls and apocatastasis. For this reason D. became involved in the repeated condemnations of Origenism, and his works were for the most part lost.
As a writer, D. shows no concern for elegance of form, content to express himself precisely; moreover, he suffers from the disadvantage of having to rely exclusively on dictation. His weak, colourless, prolix style is occasionally enlivened under the influence of the fervent piety with which he discusses theological subjects.