Therefore, the Reformation is a return to the origins ( Ad Fontes) of the Christian faith and is simply a continuation of the apostolic teachings and early Christianity. The date we celebrate the Reformation as the return to the Scriptures, to what they teach. October 31st is the symbolic birthday of the Protestant branch of Christianity. However, Christ has always preserved for Himself and His true Church, a remnant of defenders and true religion promoters. The Church progressively apostatized from the true gospel of Christ. Already corrupted by various anti-Biblical practices and doctrines accumulated over the previous centuries, the Counter-Reformation was the beginning of Roman Catholic dogma's hardening. Therefore, reflecting on the Church's history, we witness the tragic compromise and corruption of true Christianity. It is at Trent, in response to the Protestant-Reformation, that through its Counter-Reformation, the Pope, with his supporters, codified the official Roman Catholic beliefs.
Today's Roman Catholic doctrine was organized during the Council of Trent (1545-63 AD) and then restated and, to some extent, refined during the first and second Vatican Councils (1869-1870 AD, 1962-65 AD). The Church of Rome, as we know it today, is the result of a constant drift away from scriptural truth which began around the fourth and fifth century AD, during the "Christianization" of the pagans. The Bible is clear salvation is received by grace alone, through faith alone, and rests only on the person and work of Jesus Christ alone (Eph. Roman Catholics who base their salvation on divine grace + human merit, faith + human works, or Christ + the magisterium of the Roman church, can never be sure of their salvation since they are merely grounding their salvation not on God alone (absolute certainty par excellence), but man. Moreover, the Bible speaks of the assurance of salvation possessed by the true believer while he is alive, which rests solely on (a) God's infallible Word (His promises to all who believe in Christ), (b) the graces in the believer's heart of which the Word speaks, and (c) on the testimony of the Spirit of God which enables the believer to confirm the one (the Word) through the others (the graces). If alongside the person and work of Christ, man's meritorious works are included in salvation, then, precisely because man is by nature evil, deceptive, fallible, and unreliable, no one can experience the biblical and infallible assurance of salvation. True believers who trust in the sufficiency of the saving work of God in Christ are trusting in the objective, certain, authoritative, infallible, and immutable promises of God. The believer's assurance is further strengthened and confirmed by the Spirit of God's continuing work in the believer himself, which begins with the effectual call and ends with glorification. Thus, Christ's saving work is itself the sole foundation of their saving faith. God makes promises to those who believe, and true believers rest on God's infallible promises in Christ, founded solely on Christ's person and works. Still, the Bible speaks abundantly of the assurance of salvation that every true believer can and should possess. If you ask a Roman Catholic (and even some evangelicals) the question: "are you saved?" the inevitable answer is: "Who knows? Only God knows!"