AMBROSIASTER. - A fictitious name, coined by Erasmus of Rotterdam, to designate an ancient anonymous Christian writer, until then identified with St. Ambrose of Milan.
Erasmus was the first to discover that the famous Commentary on the Epistles of St. Paul, traditionally attributed to St. Ambrose, was not by Ambrose. And since he thought that the same actual author of the Commentary was responsible for the false Ambrosian attribution, for this reason he applied to him the derogatory name of A., or false Ambrose.
This particular opinion of Erasmus does not seem to be supported by recent investigation, but the discovery of the difference in authorship of the Commentary remained established in patristic scholarship.
The Works. - Various other writings have recently been attributed to the A., of which only two are to be considered interauthentic: the pseudo-Augustinian Quaestiones Veteris et Novi Testamenti, and some anonymous exegetical fragments on St. Matthew. The other claims, due in part to Morin, in part to Wittig, are devoid of serious foundation, when they are not outright in conflict with the authentic work of the A.
The Commentaria in XII Epistolas b. Pauli (except that to the Hebrews, which according to the A. is not by St. Paul) are, in the judgment of ancient and modern scholars, one of the best and most sober patristic interpretations of Pauline thought. The critical edition, on which work has been underway since the early years of this century, is still awaited. Nevertheless, thanks to the paleographic examination recently pursued by Souter, a fact has come to light that does not appear from the existing editions (cf. PL 17), namely the variety of recensions in which the work has been transmitted to us. There are in fact three recensions of the commentary on Romans, two of the commentary on Corinthians, while the others exist in a single form. The critical edition of the commentary will be contained in two volumes of the Vienna CSEL.
With the Commentaria, the book of Quaestiones presents profound and innumerable affinities of thought and form, a very interesting collection of exegetical, polemical (e.g. against Porphyry) and speculative treatises. Of this work too the manuscripts transmit three recensions, of which however only two, one of 127, the other of 151 treatises, are authentic. The critical edition edited by Souter (CSEL, 50 [1908]), apart from its great merits, is nevertheless to be considered insufficient as regards the twofold recension of the Quaestiones. In fact Souter publishes in full only the "127" Collection, which, in his judgment, represents the second edition revised and corrected by the A. It is to be believed, however, that this Collection contains only in part the second edition. The other part must be sought in the "151"; for which reason it is still necessary to make use of Migne (PL 35, 1207-1416).
Besides the two aforementioned works, there also belong to the A. not only the long eschatological fragment on Mt. 24 and the shorter De Petro Apostolo, but also the very brief De tribus mercuris, all three preserved in cod. Ambros. I, and published by G. Mercati in Studi e testi, 11, 1, Rome 1903, pp. 23-49.
The Author. - From these writings there emerges a well-defined personality of an original writer, a sober exegete attached to the historical-grammatical sense, a vigorous but reasonable polemicist, a theologian not very profound but of clear ideas. Certainly Western, and of Italian or Spanish origin, probably converted from paganism, he writes at Rome under the pontificate of St. Damasus (366-84), bringing to his literary work a legal mind and an uncommon knowledge of paganism as of Judaism. It seems that he held the rank of presbyter in the Roman curia.
As for his identification, the testimonies both internal and external are silent. St. Jerome, who shows that he knows a treatise of the A. (Quaest. 109; cf. Epist. 73, of 398), is ignorant of its author. The names of St. Ambrose, St. Hilary, St. Augustine from the manuscript and literary tradition are nothing but conjectures of the ancients. But equally failed are all the attempts to unveil the anonymous, made by modern scholars. The A. is neither Tyconius, proposed by Morel, nor Hilary the Roman deacon, the opinion dominant in the last century, nor Faustinus the presbyter, suggested by Langen, nor finally Isaac, the converted Jew, a name proposed among many others by Morin, although it has met with great but unjustified favor among some critics.