"There was one Gospel for 1500 years in both the East and West, and it was not Protestant in any way" ?

There was once a thread over on a discussion board in which one of those "I'm going to join the Roman Catholic Church" announcements was put up. In the thread, a Roman Catholic made the following statement:

The "biblical Gospel" is the Catholic Faith. Once again, I shall remind you (for perhaps the 100th time now) that there was no Evangelicalism nor Protestantism prior to 1517. There was one Gospel for 1500 years in both the East and West, and it was not Protestant in any way.

Statements like this carry assumptions that often don't get challenged. For instance, what was the official Roman Catholic teaching on justification in 1517 or previously? What was the official definition of that "one Gospel"? If there was one consistent biblical gospel taught by the Roman Church, evidence of it should be easy to document. I challenged this particular Catholic to provide such evidence, and well, let's just say a week or two went by so I shut off the lights, locked up, and went home.

The confusion of the Roman Catholic Church on this issue can be seen by looking at two 16th Century Roman Catholics previous to Trent. Alister McGrath discusses Gasparo Contarini and Paolo Giustiniani as an example of the confusion over justification during this time period. Both men were members of a group of Paduan-educated humanists. McGrath notes that Giustiniani chose to enter a local hermitage to have sin expiated (a retreat from the world), while Contarini remained "in the world" believing salvation can't mean such a retreat. Both men corresponded with each other. McGrath states:

The Contarini-Giustiniani correspondence is of importance in that it illustrates the doctrinal confusion of the immediate pre-Tridentine period in relation to the doctrine of justification. Giustiniani was convinced that it was necessary to withdraw from the world and to lead a life of the utmost austerity in order to be saved, whereas Contarini came to believe that it was possible to lead a normal life in the world, trusting in the merits of Christ for salvation. But which of these positions represented, or approximated most closely to, the teaching of the Catholic church? The simple fact is that this question could not be answered with any degree of confidence. This doctrinal confusion concerning precisely the issue over which the Reformation was widely held to have begun inevitably meant that the Catholic church was in no position to attempt a coherent systematic refutation of the teaching of the evangelical faction in its crucial initial phase. (Alister McGrath, Iustitia Dei: A History of the Christian Doctrine of Justification (Third Edition) [Cambridge: Cambridge University Press, 2005], 311.

Revised 07-25, editing.