"Theodore of Mopsuestia (ca. 350-428) wrote a book titled Against the Defenders of Original Sin which Saint Photios the Great read and reviewed in his Bibliotheca (177). It is often said that Theodore was the only eastern bishop who not only spoke about but also against Original Sin as formulated in the West, but with this review we see that Saint Photios does as well. The chief defender of the doctrine of Original Sin, according to Theodore, was someone named "Aram", which scholars today mostly agree refers to Saint Jerome. However, Saint Jerome defended the doctrine of Original Sin primarily as a reaction to the extremes of Pelagianism, following in the footsteps of Saint Augustine. In actual fact, it was Saint Augustine who formulated the doctrine of Original Sin, also as a reaction to the extremes of Pelagianism, which is why Fr. George Florovsky writes of this book, "Theodore wrote against St. Augustine’s doctrine of original sin." Saint Photios was clearly unaware of both Saint Augustine's and Saint Jerome's defense of this doctrine, which he views as an obvious heresy foreign to the teachings of the Church and an extreme reaction against Pelagianism.
Seeing that he praises Saint Augustine elsewhere in his writings, one wonders what he would have said about him if he knew that it was he who formulated this heresy. For pointing out the errors of these anonymous defenders of Original Sin, which were primarily Saint Augustine and Saint Jerome, Theodore of Mopsuestia is praised by Saint Photios, however Theodore also takes a wrong turn at points and falls into Nestorianism and Origenism and Pelagianism, which Saint Photios also discerned and condemned. Further, Theodore clearly embellished some points about Jerome in particular to make him look worse and supplement his argument. Unfortunately, everything we know of Theodore of Mopsuestia's book Against the Defenders of Original Sin comes from this review of Saint Photios and some fragments that alone have come down to us. Below is the excerpt of Saint Photios' review dealing with this book against Original Sin, to show how he condemned without hesitation this "new" false doctrine as something foreign to the Church.
Read a book whose subscription reads, "Theodore of Antioch, Against Those Who Say That Men Sin by Nature and Not by Intention." His polemic against those is developed in five books. He wrote this work against westerners touched by this ill; it is among them, he says, that the promoter of this heresy appeared: he left the west and came to establish himself in eastern regions and there composed some books on the new heresy which he had imagined, and sent them to the inhabitants of his country of origin. By these writings, he attracted many people of those regions to adopt his views to the point where entire churches were filled with his error.
I cannot say with certainty whether the name of Aram which he gives to their chief is a name or nickname. This person, the author says, fashioned a fifth gospel which he feigns that he found in the libraries of Eusebius of Palestine. He rejected the translation of the New and the Old Testament published by the united Seventy and also those of Symmachus, Aquila, and others, and boasted that he had composed a new one of his own without, like the others, having studied and practiced Hebrew since infancy and without having mastered the spirit of the Holy Scripture. Instead he put himself under the tuiton of some low-class Jews and there acquired the audacity to make his own version.
The principles of their heresy are, in summary, the following. Men sin, they say, by nature and not by intention; and "by nature" they do not mean that nature which was in Adam when first created (because this, they say, was good because it was made by a good God), but that nature which was his later after the fall because of his ill conduct and sin. He received a sinful nature in exchange for the good and a mortal nature in exchange for an immortal; it is in this manner and by nature that men became sinners after having been good by nature. It is in their nature and not by a voluntary choice that they acquired sin.
The second point is connected to the preceding propositions. They say that infants, even newly born, are not free from sin because, since the disobedience of Adam, nature is fixed into sin and that this sinful nature, as was said, extends to all his descendants. They quote, he says, the verse, "I was born in sin" and others similar: the holy baptism itself; the communion with the incorruptible body for the remission of sins and the fact that these apply to infants they view as a confirmation of their own opinion. They claim also that no man is just, and this is thus obviously a corollary of their initial position, "because nothing of flesh can be justified before you," he says, and he cites other texts of the same kind.
The fourth point - O blasphemous and impious mouth! - is that Christ himself, our God, because he put on a nature soiled by sin, was not himself free from sin. However, in other places in their impious writings, as the author says, it can be seen that they apply the Incarnation to Christ not in truth and in nature, but only in appearance. The fifth point is that marriage, they say, or the desire of carnal union and the ejection of seed and all that is of that domain and by which our species perpetuates itself and increases itself are works of the evil nature into which Adam fell through sin to receive all the weight of the evils because of his sinful nature. Such are thus the positions of the heretics.
As for our Theodore, he refutes them with reason and sometimes it is in the best manner and with vigor that he blames the absurd and blasphemous character of their opinions; and, in returning to the words of Scripture that the others interpret against their correct meaning, he demonstrates their ignorance perfectly. On the other hand, this is not always the case, but he seems to us, in many places, entangled in the Nestorian heresy and echoes that of Origen, at least in that which concerns the end of [eternal] punishment. Further, he says that Adam was mortal from the beginning and that it was only in appearance, to make us hate sin, that God seemed to impose death on us as a punishment for sin; this assertion does not seem to me to proceed from just reasoning, but on the contrary it leaves much to explain if someone chooses to ask, even if, as the author wants to say, a opinion like his is strongly opposed to heresy. Because an idea is not good just because it fights a bad idea - in fact bad ideas combat each other - but that which conforms to valid reasoning and is supported by the testimony of the holy Scriptures is admissible, even if no heresy dares to oppose it."