St. Jerome translated the Vulgate Bible from copies of Greek and Hebrew manuscripts in the late fourth century. It was one of the most important accomplishments in his lifetime. This was not the first Latin translation of Scripture but it quickly became the accepted version used by the Church and all of Christendom. Before his translation there were many versions of the Old Latin or Vetus Latina manuscripts floating around, (approximately 27) and a more readable accessible version was needed.
So, St. Jerome translated the Bible (both New and OT) into the common Latin, the vulgate, the language of the people of the ancient world.
As he neared completion of this monumental task, he came to the second chapter of the book of James and read this in the original Greek manuscript he was translating from:
"Ye see then how that by works a man is not justified, and by faith only." (Jam 2:24)
He was troubled by this verse because it didn’t express what he felt was James true intention of the spirit of the chapter. Perhaps he thought, the original Greek manuscript had an error! St. Jerome, being a theologian knew what the Catholic Church stance was regarding faith and works. He knew that the Catholic Church believed that faith alone was not part of their doctrine. He knew that Catholic soteriology expressed that good works done in this life were an important aspect of final salvation. So he pondered , prayed and researched. He was beside himself because this manuscript was stating the opposite of what he knew to be true Catholic doctrine. His first thought was to just declare this book "un-inspired" and place it in the same category of the deuterocanonicals he struggled with. (thereby relegating it to an apocryphal status.) Finally, he decided that it would be in the "spirit of St. James" to add the word “not” before we are justified by faith alone. He merely had to take the not (ouk) from in front of justified (dikaiontai) and place it in front of the word faith. Just a simple transposition of a single word. After all, he was a theologian which much more learning than the average person and he felt that he had the authority to do this, given his tremendous education and position of responsibility in the Church. He even went up against the pope at one point trying to convince him the deuterocanonicals weren't inspired, (but he was corrected and submitted to the authority of the Church) He felt that he knew what James was trying to express here and thought he could make it clearer by switching the words around a bit. In a more quiet moment, St. Jerome pondered whether anyone else in salvation history would ever consider making this same bold decision to add or subtract from the Word of God. When he finished his translation of the Greek NT into the Vulgate Latin the "translated" verse read like this:
"Ye see then how that by works a man is justified, and not by faith only."
This small alteration of the original text would hardly be noticed by anyone and would be more in keeping with the Catholic view of faith and works. As a matter of fact, the Vulgate translation of St. Jerome was recognized as the "official" Bible translation of the Catholic Church at the Council of Trent. It had been used and accepted by the Church since the fourth century and three other councils had already approved it but this was stated at Trent in response to the reformer's attempts to discredit the canon of the Catholic bible. Most importantly it contained that pivotal verse in James that the Catholic theologians so often use to defend their soteriology against the sola fide of the reformer.
This is a tongue in cheek post, just in case anyone didn't realize it by now.
St. Jerome would not have presumed to know the mind of the writer of Scripture and would have never attempted to add or subtract words in order to make scripture express his view more clearly. In his own life, he had strong opinions regarding which books of Scripture were inspired but ultimately submitted his will to the Church, the pillar and foundation of Truth.