Dictionary of Christian Biography and Literature to the End of the Sixth Century/Marius Mercator, a writer
Marius (1) Mercator, a writer, of whom,
until the last quarter of the 17th cent., nothing was known except
indirectly through the writings of St. Augustine, who in his work de
Octo Quaestionibus Dulcitii, mentions him as his son, i.e.
his friend or pupil, and who addressed to him a letter, containing a
long passage identical with one in that work (Ep. 193, de
Oct. Quaest. Dulc. qu. 3).
Probably a native of Africa, in Rome in 417 or 418, and thought by Baluze to have outlived the council of Chalcedon, a.d. 451. When Julian of Eclana was lecturing at Rome in 418 in favour of Pelagianism, Mercator replied to him, and sent his reply to St. Augustine, to whom not long afterwards Mercator forwarded a second treatise. Whether these two works exist or not is doubtful, but a treatise called Hypognosticon, or Hypermesticon, in six books, included in vol. x. of St. Augustine's works (ed. Migne, p. 1611), has been thought to be the one in question. Five of the books treat of Pelagianism, and the sixth of Predestination. The letter of Augustine, forwarded by Albinus, a.d. 418, expresses admiration of the learning of Marius and discusses points submitted for consideration.
The works of Marius Mercator, being chiefly translations, some of them from his own writings in Greek, appear in Migne in the following order, together with much matter more or less relevant to the principal subject. Part I. 1. Commonitorium super nomine Coelestii.—A memorial against the doctrines of Coelestius and Julian, disciples of Pelagius, written in Greek, and presented by Mercator to the emperor Theodosius II. and to the church of Constantinople, a.d. 429, translated by himself into Latin. It contains a history of Pelagianism and an account of its doctrines, and an appeal to Julian to abandon them. 2. A treatise, to which the Commonitorium is a preface, against Julian, entitled Subnotationes in verba Juliani, written after the death of Augustine, a.d. 430. 3. Translations of various works relating to Pelagianism, including the creed of Theodore of Mopsuestia, with a preface and a refutation of the creed by Mercator. Part II. Concerning the Nestorian heresy, including extracts from Theodore of Mopsuestia, with preface and refutations by Mercator. Extracts from Theodoret bp. of Cyrus, against Cyril, and from his letters, with remarks by Mercator.
Marius Mercator appears to have been a layman, but an able theologian. His learning, zeal, and ability entitle him to a respectable place among ecclesiastical writers. Migne, Patr. Lat. xlviii.; Ceillier, viii. 36.
[H.W.P.]