The question of whether a believer can have assurance of their salvation in this life is a vexed one among Christians. The Roman Catholic or Eastern Orthodox Christian is likely to regard the Lutheran claim of assurance of salvation as presumptuous; this judgment is based on their underlying assumption that our faith is to be supplemented by works of love. Since no-one can be sure that the quantity and quality of their works meets with God's approval we must await God's post-mortem judgment upon our life before we can be certain of our eternal destiny.
On the other hand, the Lutheran regards the Catholic or Orthodox denial of the possibility of assurance of salvation in this life as presumptuous, since it calls into question the completeness of Christ's saving work on behalf of sinners and teaches that our Lord's work must be supplemented by our works in order to be efficacious for eternal salvation. As the quote prefacing this post shows, Luther was strongly critical of the denial of the possibility of assurance in the late medieval church; it could even be said that Luther's quest for assurance of salvation was the matrix of the Reformation. While there may be points of misunderstanding in this matter that can be clarified through discussion, surely the two positions are fundamentally opposed and hence irreconcilable, even for the most deftly ambiguous of ecumenical theologians.
While discussions on this question usually come to focus on the place and value of works in the justification of the believer, a question we will come to shortly, it seems to me that the real nub of the problem is that Roman Catholics and Eastern Orthodox do not fully grasp the proleptic nature of God's judgment upon the believer in Christ (proleptic = a future act made present). This was brought home to me when I recently read a Russian Orthodox writer on the matter who opined that we can never have assurance of salvation in this life because we cannot judge ourselves - only God can judge us. This view, I submit, represents a fundamental failure to grasp the reality of God's work in justifying the ungodly (Oh, the irony...it is usually Catholics and Orthodox who claim the Lutheran doctrine of justification is a "legal fiction"!).
In Romans, the apostle Paul writes, “But now, apart from the law, the righteousness of God has been made known, to which the Law and the Prophets testify. This righteousness is given through faith in Jesus Christ to all who believe” (Romans 3:21-22). Catholic and Orthodox Christians do not grasp the fact that God has already judged believers in Christ and has not only pardoned them but declared them righteous for Christ's sake. It is on this basis - the active (keeping the Law) and passive (suffering for our sins) righteousness of Christ - that the Lutheran's assurance of salvation rests and not on any presumptions about the quality of his or her works of love. Works of love done in grateful and joyful service to God and our neighbour are the the fruit of justifying faith in Christ, not a contributing factor in the believer's justification, which is all of grace because of Christ ("We love because he first loved us" 1 John 4:19; cf the whole passage from vv10-24). Interestingly, by a felicitous inconsistency, the Eastern Orthodox funeral service does not commend the deceased to God on the basis of their works of love but appeals to His mercy which derives from His love for us in Christ.
There is more than can be said, particularly on the individual believer's judgment upon death and the role of works and reward in that judgment, but I will leave that for another time. I would be grateful for any comments from Catholics or Orthodox. After a month of not attending to the blog for various reasons I just noticed that my last post on the infallibility of church councils (a topic I hope to return to soon, D.v.) was one of the most read ever posted on this blog, but no comments were received; I'm always grateful for and will post constructive comments that test my arguments.
* Cited in Stephan H. Pfuertner, Luther and Aquinas, A Conversation (Darton, Longman & Todd, London, 1964, p120).