I was reading an essay today on a meeting between the catholic church and the reformers (specifically Melanchthon and Calvin were present) to try to bridge their theological gap. It was one of several such meetings. While ultimately the meetings were unsuccessful, they did manage to produce consensus on the nature of man and original sin and, surprisingly, justification. The meeting was known as the Regensburg Colloquy and it was article V that dealt specifically with justification.
While the document has some flaws, it is truly remarkable because you can scarcely believe what the Catholics agreed to!
Here is a sampling:
(3-6) By this faith [man] receives... imputation of righteousness and countless other gifts.
(4-4) "So living faith is... believing that the righteousness that is in Christ is freely imputed to it..."
(5-1) "Although the one who is justified receives righteousness and through Christ also has inherent [righteousness],... the faithful soul depends not on [inherent righteousness], but only on the righteousness of Christ given to us as a gift,"
A word about that last quote. The Catholic understanding of the day was that through faith the grace of God transforms us into better and better men. And this is what we call inherent righteousness. It was long assumed that this is the righteousness that God counted, namely our own. Granted it came from God. But here we find the stunning turn that the Catholic Church (and this was official representatives of the Pope) grants that we are justified by grace through faith because we have the righteousness of Christ imputed to us. They also agree that there is another kind of righteousness which is called "inherent righteousness". This is best thought of as the righteousness that is inherent to a man as by God's grace he is transformed. It is pretty close to what we would call sanctification. So here you have the Catholic Church finally separating justification from sanctification.
Now the document isn't perfect and Luther, who was not present, refused to endorse it. But Calvin did, and Melanchthon was a debater. What is sad is that once this enormous barrier was crossed they basically came to a complete standstill. I suppose that it was so early in the theological development that neither side (especially the Catholics) had grasped the full implications of this key doctrine. Can you imagine Rome signing this document again today. That, indeed, would be a huge step toward ecumenism.