Perseverance of the saints (POTS) is a teaching that is built on the reformed doctrines of election and predestination that are held by nearly every Calvinist. If you would like to read the definition of this belief you can check out this teaching in the Westminster Confession and The 1689 Baptist Confession.
Michael Milton, the Chancellor of Reformed Theological Seminary also includes "the progression in holiness" as part of the doctrine of POTS. There are, in my opinion, some problems with the idea of perseverance and progressing in holiness, namely, what if we are not progressing in holiness? Furthermore, what does that even look like? First Samuel 2:2 says "There is none holy as the Lord" and Romans three makes it clear that there are none righteous, no not one. Is it really possible to be able and quantify perseverance and progressive holiness? It all seems pretty subjective to me.
The basic premise of POTS is that because God only saves those whom He has predestined to be saved, also known as the elect, God also grants to these elect the ability to persevere in faith until the end of their life. The problems arise for many folks when the question is asked "What if an alleged believer falls away and no longer perseveres in faith? Are they still saved, are they really elect?" The answer comes from logic, the Word of God and the honest, knowledgeable Calvinist. The answer is you cannot be sure that a person is really one of the elect if they lapse or fall away. The answer is we don't know for certain if that person is saved. The Westminster Confession and the 1689 Baptist Confession allow for the possibility that a believer can lapse into sin "for a time" but that a true believer, truly called and elected, will come back on the path of perseverance and "renew their repentance". Another question to consider is what is "a time"? How long can I slip up before it becomes apparent that I'm not one of the elect? 
The doctrine of POTS provides no assurance of salvation. Let me put it another way, the doctrine of POTS provides no certainty of eternal life because according to this dogma no one can truly know that they are going to persevere to the end. In some more recent research on assurance of salvation, under half of professing Christians feel certain that because of their faith in Christ they will inherit eternal life.That means that the majority of Christians are not sure of their standing with God.
Calvinists, if they rightly understand their reformed teachings, cannot have real assurance of their salvation and most of them don't!
Several years ago I read about a Presbyterian pastor in the south that was dying of cancer and in the final weeks of his life requested prayer from his friends and family that he would "die in the faith". I felt that it was tragic that a man who preached for 50 years, wrote books and counseled thousands, had no assurance that he was saved! He was basically asking his prayer partners to pray that he would persevere.
Another way of looking at this from the reformed perspective is if you are a professing believer who falls away and never gets back on the perseverance pathway then the only conclusion that can be drawn is that you were never a believer in the first place.
Quite frankly, there is not much difference between the Calvinist position on salvation and the Arminian position. The Arminian says that if you place saving faith in Christ then fall into sin you are in danger of losing your salvation. The Calvinist under the same circumstances says that you were never a believer in the first place. I really don't see a meaningful difference between the two positions.
The evidence that one is persevering in the Faith is very subjective in the reformed doctrine of POTS. This lack of concrete clarity has caused some wild new sub-doctrines to spring up in recent years. Take for instance, John Piper's doctrine of "final salvation". Piper, a reformed Baptist, says that we are initially justified by faith alone but we will be "finally saved" by the fruit we produced, you can read his own words here.
I found this sermon to be profoundly confusing. How can anyone truthfully say they have assurance of salvation if they believe they are only living in phase one of their salvation experience? What will the final salvation judgement be like? If this situation was really possible we could never really know if we would attain final salvation. Logically we must conclude that Piper teaches a final salvation by works.
The doctrine of POTS is not the same as the doctrine of "eternal security". The doctrine of eternal security, also known as once saved always saved (OSAS) is fast becoming a very rare commodity among our churches in these last days.
I will start my defense of the doctrine of eternal security by addressing something that is rarely taught in so many of our churches today. I place a high value on the Gospel of John because it is the only book in the Bible that states it's purpose to be Evangelical, it is the only book in the Bible that has as its main is to lead the reader to believe in Jesus for eternal life.
Here is what it tells us in the 20th chapter of John, verses 30-31. "And many other signs truly did Jesus in the presence of His disciples, which are not written in this book: but these are written, that ye might believe that Jesus is the Christ, the Son of God; and that believing, ye might have life through His name."
The Gospel of John has been called the Gospel of belief. John 5:24, John 3:16 and a host of other verses in John indicate clearly that the sole requirement to attain eternal life is to believe in Jesus for it!
Notice that I said we must believe in Jesus "for eternal life". Eternal Life is the reward for simply believing.
Zane Hodges was a New Testament professor at Dallas Seminary before his passing in 2008. Zane is cited by Dr. Bob Wilkin's book The Gospel Is Still Under Siege on pages 11-12...
Zane Hodges said assurance is "part of God's offer" and is "the clear intent of the Gospel proclamation." He indicated that to suggest otherwise "flies in the face of the offer of eternal life made by the Son of God Himself." Hodges cited John 5:24, which has three promises concerning the person who believes in Jesus; 1) he has (present tense) everlasting life; 2) he will not come into judgement (future tense) regarding everlasting life; and 3) he has passed (past tense) from death into life.
Wilkin rightly concludes that everlasting life is not merely a result of believing in Jesus but it is what we believe in Him for!
OSAS teaches that when a person believes in Jesus for the promise of everlasting life he acquires that gift immediately and it is irrevocable. It can never be forfeited by the believer, it is never dependent upon a believers efforts. Eternal life is irrevocable and this brings true assurance. Assurance is of the essence of eternal life.
I will make a statement that will no doubt upset many of my Calvinist and Arminian readers. If you have never believed in Jesus for eternal life that can never be lost then you have never been saved. To not believe in eternal security is to believe that there is something you must do to secure it. That my friends, is not Faith alone!
Remember John 5:24? The man, woman, boy or girl who believes in Jesus for everlasting life "hath" everlasting life, will never be under condemnation and has passed from death into life!
The chief complaint levied against this OSAS position by reformed folk is that those who believe in OSAS will live like the Devil and never pursue holiness. Nothing could be further from the truth. One passage of Scripture that captures the truth of dedicated living for Christ is found in Second Corinthians 5:14-15..."For the love of Christ constraineth us; because we thus judge, that if one died for all, then were all dead: And that He died for all, that they which live should not henceforth live unto themselves, but unto him which died for them, and rose again."
When we properly understand the great promise of forgiveness, eternal life and security given to us freely through faith we are "constrained" to live for Him!
It would be good that Calvinist and Free Grace people would look to gratitude as a motivation to good works and holiness. The church at large has also neglected to teach and preach about rewards at the BEMA Seat Judgement which is also another powerful motivation to live for the Lord.
There is a vast difference between POTS and OSAS! POTS offers no certainty of final Salvation. OSAS provides, as the hymnist so beautifully wrote, blessed assurance Jesus is mine!
A few years ago my wife and I were searching for a church to attend and join. We found a Baptist church in the nearby town of Ottawa, Kansas. We both enjoyed the hymns they used in worship and the structure of their worship service. However, there we comments the pastor made from time to time that caused me to question whether he had some reformed leanings.
After several Sunday visits to the church the pastor offered to come by and visit us in our home. We had a pretty good visit and at the end the pastor asked if I had any questions and I said that I had one question. I asked this pastor, "What do you base your assurance of salvation upon?" The question seemed to take him a little by surprise. He stared at the ceiling for a moment and then he said, "I think I would have to examine my life and see how I've been living." I thanked him for his honesty and then I shared that I was basing my assurance of eternal life on the promises of God's Word.
The question I asked revealed the pastor's belief in POTS. My wife and I began a new church search the following Sunday!
It's not Semantics! There is a great chasm between perseverance of the saints and once saved always saved (eternal security). There is such a thing as final Salvation too, and it happens the moment someone believes on Jesus Christ for eternal life!
