Saint Prosper of Aquitaine (390-463) was a layman, disciple of Saint Augustine, a man of great doctrine and knowledge. He was a secretary of Pope Leo the Great. Most of his writings deal with heresies that were rampant in those days, especially Pelagianism, a doctrine that affirmed that original sin does not affect men to the point of being to able to choose between good and evil without divine grace.
An important work by Prosper was his Chronicle: “The Chronicle of Prosper, from the creation to 378 AD, was an abridgment of St Jerome’s, with, however, some additional matter, e.g. the consuls for each year from the date of the Passion. There seem to have been three editions: the first continued up to 433, the second to 445, the third to 455. This chronicle is sometimes called the Consular Chronicle, to distinguish it from another ascribed to Prosper where the years are reckoned according to the regnal years of the emperors and which is accordingly called the Imperial Chronicle. This is certainly not the work of Prosper. It was compiled by a man whose sympathies were not with St Augustine.
The story that Prosper was Bishop of Reggio in Italy was refuted by Sirmondi and others in the 17th century. For the origin of this legend see Dom Morin in Révue bénédictine, XII, 241 sqq. Prosper was neither bishop nor priest. The question whether he mitigated the severity of St Augustine’s doctrine has been much debated. The difference of opinion probably arises more from different views regarding St Augustine’s doctrine than from different interpretations of Prosper’s. The general trend of opinion among Catholic writers seems to be in favour of the affirmative view, e.g. Kraus, Funk, Bardenhewer, Valentin, and others.” (Bacchus, F.J. (1911). Tiro Prosper of Aquitaine. http://www.newadvent.org/cathen/12487a.htm).
In their introduction to this book by Prosper, the scholars Johannes Quasten and Joseph C Plumpe attest: “Our treatise examines the problem of the salvation of all men from a double aspect. If God’s salvific will is universal and of this there can be no doubt how is it that many are not saved, or, as the author prefers to view it, how is it that many do not receive the grace that saves (Book One)? And inversely, if many are not saved or do not receive the grace that saves, how can there really be in God a universal salvific will (Book Two)? The problem is difficult, and, especially in Prosper’s time, it was a delicate one to tackle. St Prosper proposes to explain the doctrine of God’s universal salvific will. But it so happened that St. Augustine had not, or, at any rate, had not clearly, taught a universalist doctrine about God’s will of salvation; rather, he had repeatedly interpreted the Scripture texts about God’s will to save men, in a restrictive sense.
On the other hand, the Semi-Pelagians, Prosper’s opponents, forcefully stressed the universality of God’s salvific will in order to drive home their point regarding the initiative of man’s free will in the work of salvation. St Prosper had therefore to steer a middle course between these two extremes. Against Semi-Pelagianism he had to assert the absolute gratuitousness of grace, but in such wise as to safeguard a real universal salvific will. On the other hand, in spite of St Augustine’s teaching, he had to maintain the universalism of God’s will to save men, without, however, impairing the gratuitousness of grace; this gratuitousness he held, with Augustine, to be the Catholic doctrine.”
As we can see easily, these are themes that still today are deeply relevant and subject to countless conversations and debates in many theological and philosophical circles.