The privilege of assurance, which is secured by the work of Christ for His own and which is properly undergirded in the Reformed faith, is damaged or even destroyed in certain other theological structures.
I. When justification by faith alone is not duly proclaimed and the good works of the believer are presented as participating in the ground on the basis of which salvation is secured, the assurance of faith receives a fatal blow. The prime example of this distortion is found in the official doctrine of the Roman Catholic Church as prevalent in the time of the Reformation and codified at the Council of Trent (1545–1563).
In this view it is not denied that Christ has accomplished a saving work for humanity, but justification is envisioned as the total process by which the redeemed are brought to perfection by the Holy Spirit. To say, then, "I am justified" is equivalent to a claim of having achieved perfection. Who can realistically make such a claim? Nobody! Those who venture to do it are adjudged to be arrogant and presumptuous. The best that can be said is: "I am in the process of being saved; I hope that at the end of my life I may be in a state of grace and therefore not cast into hell; I am diligently seeking to take advantage of the means of grace (sacraments) and to refrain from sinning, but God only knows whether I am going to make it."
It is this uncertainty that drove Martin Luther almost out of his mind before he came to understand the great truth of justification by faith alone. At last he perceived that salvation is not secured by dint of good works, fastings, alms, and other disciplines, but that it has been purchased in full by the saving work of Jesus Christ with whom we are united through faith alone. The fact of this union brings with it assurance just as an authentic receipt brings complete release from the burden of a debt.
It is to be noted that the Roman Church is not the only offender in this respect; many groups and individuals have also clouded the pure doctrine of justification by introducing an element of human merit in the process. Even many Lutherans, otherwise orthodox, have shown reluctance to confess the perseverance of God with the redeemed, and thus made a present assurance no guarantee of an ultimate salvation.
II. This problem also burdens the Arminian view. In keeping with Arminian principles, a believer may properly say, "I am saved now," for by virtue of the work of Christ God confers salvation to any and all who repent and believe. Yet this blessing is not a basis for complete confidence that a change of disposition may not occur. There are many tragic examples, they say, of people who after having been saved have turned away and lost out altogether. The apostle Judas is a notable case in point, and Hebrews 6:4–6 surely provides a solemn warning in this respect:
It is impossible for those who have once been enlightened, who have tasted the heavenly gift, who have shared in the Holy Spirit, who have tasted the goodness of the word of God and the powers of the coming age, if they fall away, to be brought back to repentance, because to their loss they are crucifying the Son of God all over again and subjecting Him to public disgrace.
If salvation once experienced is not secured by the grace of God so as to be a permanent blessing, the momentary assurance of it is of relatively small significance. Even those who, in Arminian terms, have experienced "Christian perfection" are not immune from the danger of falling from grace and being lost.
Although Arminians seldom reason it this way, it would appear that for them the best thing that could happen would be to die as soon as they have accepted Christ. To continue to live is to expose oneself to the risk of losing salvation. This is certainly not Paul's outlook in Phil. 1:22–26:
If I am to go on living in the body, this will mean fruitful labor for me. Yet what shall I choose? I do not know! I am torn between the two: I desire to depart and be with Christ, which is better by far; but it is more necessary for you that I remain in the body. Convinced of this, I know that I will remain, and I will continue with all of you for your progress and joy in the faith, so that through my being with you again your joy in Christ Jesus will overflow on account of me.
III. There are, of course, other systems of thought that undermine assurance in a still more fundamental way. For instance, those which deny the reality of life beyond the grave have no place for salvation, let alone assurance. Those also which think of salvation in social rather than individual terms do not consider assurance.
Those, finally, which expect that ultimately all rational creatures, or at least all members of the human race, will be saved extend assurance to all, but in this process emasculate the Gospel and depart from the clear teaching of Scripture as it has been well understood over the centuries.
In the Reformed doctrine assurance is grounded in the adequacy of the work of Christ, our mediator and covenant head, in the testimony of the Holy Spirit who witnesses with our spirit that we are children of God (Rom. 8:16), and in the persistent purpose of God who has begun a good work in the believer and will carry it to completion until the day of Christ (Phil. 1:6).