On April 27th, 1541, the Diet of Regensburg began. This Diet (i.e. legislative assembly) was an attempt to restore unity between the divided churches, generally recognized today as Lutherans, Roman Catholics, and Calvinists. The representatives at this Diet are particularly noteworthy, especially considering that they volunteered their efforts to publicly unify, to the best of their academic abilities, with the Roman Catholic Church. Philip Melanchthon represented the Lutherans, Cardinal Contarini and John Eck both represented the Roman Catholics, while Martin Bucer and John Calvin represented the more general "Reformed" crowd.
From this meeting arose a fascinating letter which post-reformation theologians have aptly dubbed The Regensburg Book. This book was divided into 23 articles, all of which together expressed a unified confession among the parties represented. In other words, the language of the book was such that the Lutherans, Calvinists, and Roman Catholics were all generally represented as agreeing with each other on cardinal doctrines; but even more importantly, the specific doctrinal views of Melanchthon, Calvin, Bucer, and two reputable Roman Catholic authorities agreed, as Calvin said, on "the substance of the true doctrine" of the Christian faith.
This was quite an accomplishment among the heated debates of the Protestant Reformation, and in a letter to William Farel on May 11th, 1541, John Calvin expressed the joy which this agreement brought to everyone assembled. Calvin wrote:
The debate in controversy was more keen upon the doctrine of justification. At length a formula was drawn up, which, on receiving certain corrections, was accepted on both sides. You will be astonished, I am sure, that our opponents have yielded so much, when you read the extracted copy, as it stood when the last correction was made upon it, which you will find enclosed in this letter. Our friends have thus retained also the substance of the true doctrine, so that nothing can be comprehended within it which is not to be found in our writings. You will desire, I know, a more distinct explication and statement of the doctrine, and, in that respect, you shall find me in complete agreement with yourself. However, if you consider with what kind of men we have to agree upon this doctrine, you will acknowledge that much has been accomplished.1
Regarding the doctrine of justification which Calvin noted as being vital to their joint confession, a portion from that section, translated into English, has been provided by Dr. Peter Lillback, adjunct professor of historical theology at Westminster Theological Seminary. That section can be seen below; and as many calvinists who read this will probably notice, the lack of tension between law & gospel, and imputed & subordinate-inherent righteousness is striking. I suspect that the majority of American "Calvinists" or "Reformed" Christians today would not agree with this confession:
Therefore that living faith which apprehends mercy in Christ and believes the righteousness which is in Christ has been graciously imputed to him, and which simultaneously receives the promise of the Holy Spirit and love. So then, that faith is justifying faith which is efficacious by love....Moreover, although he who is justified also receives and has through Christ inherent righteousness, as the Apostle says, you are washed, you are sanctified, you are justified, etc., wherefore the holy fathers used the word "to be justified" for receiving an inherent righteousness. Nevertheless, the believing mind does not rest upon this righteousness, but upon the righteousness of Christ alone given to us, without which there neither is nor can be any righteousness. And so we are justified by faith in Christ, or we are accounted righteous, that is, accepted through the merits of Himself, not on account of our worth or works. And we are called righteous because of inherent righteousness, because we do those things which are righteous, according to that passage in John: he who does righteousness is righteous.And although the fear of God, repentance and humility, and other virtues must always increase in the regenerated, since renovation is imperfect and great infirmities cleave to them, nevertheless it ought to be taught, that those who truly repent may always be sure by a most certain faith, they are pleasing to God on account of Christ the Mediator, because Christ is the Propitiator, High Priest, and Advocate for us, Whom the Father gave to us, and all good things with Him....Moreover, he who says we are justified by faith alone must at the same time teach the doctrine of repentance, of fear of God, of the judgment of God, of good works, in order that the whole sum of preaching might stand firm as Christ says, "...preaching repentance and remission of sins in My name," and that, lest this form of speaking be understood otherwise than it has been preached.2
Needless to say, Martin Luther, who was not present at this Diet, was not pleased with this joint confession, and so he spoke out against it. As a result of his scathing reaction, no further progress and unity was formed among the Reformed-Calvinists and the Roman Catholics.
1. Peter Lillback, The Binding of God: Calvin's Role in the development of Covenantal Theology [Grand Rapids, MI: Baker Academic; 2001], pp. 190-191. Italics mine.