On October 31, 1999, representatives of the Lutheran World Federation and the Pontifical Council for Christian Unity together executed a document entitled “Joint Declaration on the Doctrine of Justification” (JDDJ).Thus ended a 450 year division between Roman Catholic and Lutheran churches on the meaning of the Gospel of Jesus Christ. As the Declaration states:
Opposing interpretations and applications of the biblical message of justification were in the sixteenth century a principal cause of the division of the Western church and led as well to doctrinal condemnations. A common understanding of justification is therefore fundamental and indispensable to overcoming that division.
Of course, there remain sharp differences between Lutherans and Catholics, particularly regarding the role of priests, the primacy of the Pope, and the nature of sacraments. These are relatively minor disputes, however, compared to the issue of “justification”.
Justification
What is "justification"? It is many things. Indeed, it seems to be all good things that Christianity promises:
Justification is the forgiveness of sins (cf. Rom 3:23-25; Acts 13:39; Lk 18:14), liberation from the dominating power of sin and death (Rom 5:12-21) and from the curse of the law (Gal 3:10-14). It is acceptance into communion with God: already now, but then fully in God's coming kingdom (Rom 5:1f). It unites with Christ and with his death and resurrection (Rom 6:5). It occurs in the reception of the Holy Spirit in baptism and incorporation into the one body (Rom 8:1f, 9f; I Cor 12:12f). All this is from God alone, for Christ's sake, by grace, through faith in "the gospel of God's Son" (Rom 1:1-3).
JDDJ, Para. 11.
Justification is the right relationship between a human being and God. Christians contrast their justification by faith with Jewish justification by obedience to God’s law. Complete or even adequate obedience is impossible. There are over 600 commandments in the Old Testament, not just ten. No one can perform all of them: the Temple is gone, and with it the Temple cult. Ignoring the obsolete commandments (like the ones about animal sacrifice) and reducing God's law down to its essentials (Love God; Love your neighbor) only makes the problem worse. The impossibility of complete obedience is clear, stark and terrible.
Christianity’s first and foremost missionary, Paul, spread Christianity beyond Jewish enclaves. Speaking to non-Jews, he downplayed the value of obedience to Jewish law and ritual, indeed, he called it a curse. The notion that one could perfect oneself was arrogant. The Greeks understood this: they called it hubris. The idea that one could ruin one’s relationship to God merely by eating the wrong foods was terrifying. Instead, Paul preached justification as a gift: “For by grace you have been saved through faith, and this is not your own doing; it is the gift of God - not the result of works.” Ephesians 2:8.
This view of Paul’s influenced the great early Christian thinkers such as Augustine, and through Augustine it came down to an Augustinian monk in Germany named Martin Luther.
The Reformation Divide
For the Luther and the Reformers, justification by faith was the very foundation of Christianity and the assurance of salvation. Luther proclaimed Paul’s word that the just shall live by faith alone. Humanity is incapable of self-justification. The believer receives a righteousness that is not his own, but a free gift of God's grace. Entirely absent from the Reformist point of view, however, was a role for the Church in the justification of sinners. In crude terms --and these were the only terms that mattered in the political sphere-- the Church wasn't selling tickets to heaven.
The Council of Trent, in reaction, could not reject Paul. But the Church was heavily invested in a temporal role of keeping order, and enforcing moral and ethical standards. While the Church could not make obedience the ticket to heaven, it could make obedience the coin by which the ticket was purchased. Therefore, in addition to the gift of grace through faith, the Council of Trent added that the cooperation or participation of a person with his own sanctification was necessary to receive the gift. It therefore announced that Luther’s contrary view of “sola fide” (faith alone) was heresy:
If anyone says that the sinner is justified by faith alone, meaning that nothing else is required to cooperate in order to obtain the grace of justification, and that it is not in any way necessary that he be prepared and disposed by the action of his own will, let him be anathema.
Decrees of the Council of Trent, Session VII, Canon 9 (1547).
How the "Joint Declaration" Resolves the Impasse
The "Joint Declaration" affirms that justification takes place solely by God's grace, through faith. The disputants then each conceded the better part of the other's argument:
When Catholics say that persons "cooperate" in preparing for and accepting justification by consenting to God's justifying action, they see such personal consent as itself an effect of grace, not as an action arising from innate human abilities. JDDJ, Para. 20
Lutherans, for their part, had to admit that grace can be rejected, and to that extent a person’s attitude, preparation or cooperation does matter. Moreover, Lutherans admitted that they “do not deny that believers are fully involved personally in their faith, which is effected by God's Word.”. JDDJ, Para. 21
Lutherans are not about to accept the Pope as their leader, and the Church is hardly admitting that Luther was right all along, but they can at least stop calling each other heretics.
Text of Joint Declaration: http://www.cin.org/docs/cathluth.html