“If anyone says that he will for certain, with an absolute and infallible certainty, have that great gift of perseverance even to the end, unless he shall have learned this by a special revelation, let him be anathema [accursed].”
“Thus, it is not in consequence of their own merits, or strength, but of God’s free mercy, that they do not totally fall from faith and grace, nor continue and perish finally in their backslidings; which, with respect to themselves, is not only possible, but would undoubtedly happen; but with respect to God, it is utterly impossible, since his counsel cannot be changed, nor his promise fail, neither can the call according to his purpose be revoked, nor the merit, intercession and preservation of Christ be rendered ineffectual, nor the sealing of the Holy Spirit be frustrated or obliterated”
The Canons go on to talk about assurance of salvation and perseverance, stating that assurance is attainable: “true believers themselves may and do obtain assurance according to the measure of their faith, whereby they surely believe that they are and ever will continue true and living members of the church, and that they have the forgiveness of sins and life eternal.”
So far we see a stark difference between Rome’s anathema of perseverance and the Reformed affirmation of it. One more difference is found in how a Christian can be assured of perseverance. Rome says “by a special revelation.” The Reformed, however, say, “this assurance…is not produced by any peculiar revelation contrary to or independent of the Word of God,” but it comes from faith in God’s promises revealed in the Word, from the Spirit’s work within us, and from a holy desire to obey the Lord (emphasis mine). In fact, the Canons of Dort even say that true Christians have an “infallible pledge of eternal glory” – again, God’s revealed promises and the Spirit’s work in our hearts (Canons of Dort, 5.10).
To summarize, Rome has anathematized (accursed) any average Christian who believes that he or she will undoubtedly persevere in the Christian faith. Reformed theology teaches that true Christians will persevere in the faith – and can be assured of that perseverance by God’s Word and Spirit. This is one of many reasons why I am Reformed and not Roman Catholic: I do not believe the Scriptures throw us into a whirlpool of uncertainty when it comes to God’s promises of salvation in the gospel. In Paul’s words, I am sure of this, that he who began a good work in you will bring it to completion at the day of Jesus Christ (Phil. 1:6; cf. John 10:28-29 and Romans 8:28ff).