There is a very complete agreement on the part of St. Ambrose with the Catholic teaching of the universal Church. St. Augustine speaks of him as |a faithful teacher of the Church, and even at the risk of his life a most strenuous defender of Catholic truth,| |whose skill, constancy, labours, and perils, both on account of what he did and what he wrote, the Roman world unhesitatingly proclaims.| In matters both of faith and morals by his words and writings he greatly benefited the Church and was called by St. Jerome |a pillar of the Church.|
In his dogmatic treatises, more particularly in his books on the Faith, he shows great skill and penetration, and his reasoning is full and clear, meeting the most subtle objections with patient industry. Scarcely any ancient writer has treated the mystery of the Holy Trinity and the theological difficulties connected with it more clearly and convincingly than St. Ambrose in his De Fide and De Spiritu Sancto.
In his expositions of Holy Scripture he treats of the threefold sense, the literal, the moral, and the mystical, devoting more pains, however, and time to the latter than to the former. He gives special consideration to the mystical interpretation of such passages as may seem to contain in a literal sense anything diverging from sound morality. Many of his other mystical interpretations of plain, simple matters of fact have much beauty, as in his treatment of the story of the building of the ark, the marriage of Isaac, and the blessings of the Patriarchs. The literal sense is followed specially in the Hexaëmeron, the treatise on Paradise, Noah and the Ark, and the Exposition of the Gospel according to St. Luke. The moral sense, though referred to throughout his writings, is more particularly sought out in the Expositions of the Psalms.
St. Ambrose was a diligent student of the Greek writers, whom he often follows largely, especially Origen and Didymus, as also St. Basil the Great and St. Athanasius, and he has also adapted many points of allegorical interpretation from Philo. He is fond of alleging scriptural proofs, and when he argues from reason often confirms his argument by some quotation or reference, a task easy for him who, from his consecration, was so diligent a student of holy Scripture.
As to justification, St. Ambrose ascribes the whole work to the Holy Spirit, Who seals us in our hearts, as we receive the outward sign in our bodies. Through the Holy Spirit we receive a share of the grace of adoption. Christ was perfect according to the fulness of His Majesty; we are perfected by a continual progress in virtue.
With regard to baptism, he taught in accordance with the received belief of his day that it is the sacrament of adoption and regeneration, wherein sin is forgiven, and the Holy Spirit confers new life upon the soul and joins it mystically to Christ. As to the Real Presence in the Sacrament of the Eucharist, his doctrine is no less definite. In his treatise on the Faith he says of the elements that they |are transfigured [transfigurantur] by the mystery of the sacred prayer into flesh and blood.| He interprets various texts, also, in many places in the same sense. In a like spirit he maintains that the power of forgiving sins on repentance is vested in the ministry of the Church. The intercession of the saints, and up to a certain point their invocation, is likewise upheld.
There was a Latin version made from the Septuagint, including the Apocrypha, in Africa, and in use there at the end of the second century, very barbarous, and copying even Greek constructions. Of this text SS. Ambrose and Augustine used a recension. But our author seems to have been very independent, and to have made use of several different versions of holy Scripture, translating, as it would seem, often for himself from the Septuagint, referring also to Symmachus, Theodotion, and Aquila, though thinking less of the latter. When the prophets, he says, were moved by the Holy Spirit, they were troubled and darkened with their own ignorance. Prayer, he asserts, is necessary for understanding holy Scripture. Each Testament is not equally easy, and we are not to criticise what we do not understand. He speaks of the Hebrew as the truth, but states that the Septuagint added much that is useful.
The Arians are repeatedly charged by St. Ambrose with falsifying and manipulating Scripture for their own ends, not always, it would seem, very justly, but the same charge is a common one against all heretical bodies in early days. As to the Canon, he would seem to have no very definite rule. He admits Tobit as prophetic, Judith as canonical, nor does he distinguish between canonical and deuterocanonical, while the sapiential books are all attributed to Solomon. He quotes Baruch as Jeremiah, and refers to the History of Susanna, Bel and the Dragon, and other apocryphal works as |Scripture.| Ezra, he says, re-established holy Scripture by memory, and he quotes the fourth book of Esdras.