This is my Opinion on the matter not a scholarly argument etc. Just bear that in mind when you comment
Catholic patristic scholars since the 1560s have been showing that the Council of Trent's doctrine of justification is the same doctrine of justification held by St. Augustine of Hippo.
"the righteousness of God,— not that whereby He is Himself righteous, but that with which He endows man when He justifies the ungodly." - St. Augustine "On the Spirit and the Letter" Chapter 15
is the constant definition used. Now some folks like Alister McGrath say that poor Augustine didn't have Erasmus' Greek Manuscript (which had mistranslations of it's own) and that iustificare isn't the same as logozomai etc. Basically to short it to the point of triviality: Augustine was wrong, Luther was right. (Ironically another member of McGrath's church has argued that both Augustine and Luther are wrong (N.T. Wright), but there's the "perspicuity of scripture" for you)
But anyone who has read the wikipedia article on Augustine could tell you if Augustine was wrong, pardon my Anglo-Saxon but... Western Christianity is fucked, God is dead, etc...
If the Church which labelled itself as Augustinian for over a millenia was wrong about Original Sin, Predestination, Salvation, Pelagianism, Donatism, etc. Then God's Spirit is so impotent at leading the Church that there's no point in even believing.
That's my opinion. And if you think the Church was wrong about salvation for 1200 years then you might as well just become an Anabaptist and make it 1500 years, or a Mormon and make it 1800 years. Heck why not start your own church and just believe EVERYONE was wrong and it's actually justification by extrinsic interpretative-danced righteousness.
Finally: to Protestants, please give up the title Augustinian if you're just going to say he was wrong about salvation, you can't just pick and choose, even Luther said later in life that reading the bible through the interpretation of Augustine was like pouring milk through a bag of coal. So keep the title and accept infused righteousness, or give it up and keep imputed righteousness...or just remain keep your illogical idea that Augustine somehow taught what Luther taught even though he openly repudiated your doctrines.
I'm gonna regret posting this as all the Reformed will start attacking me like a Jew in the Gaza strip....and if any Jews read this I'm gonna regret posting this.