Because Calvinists believe that God shows His irresistible grace to totally depraved people whom He has unconditionally elected before time, Calvinists have no choice but to believe that it is impossible for a genuinely-saved person to forfeit his salvation. This is what the Calvinistic doctrine of the Perseverance of the Saints is all about. True saints will persevere in faith, and if they dont, they were never truly saved in the first place, according to Calvinists.
Piper certainly holds this view. Amazingly, however, at the start of his chapter about Perseverance of the Saints, he states,
Election is unconditional, but glorification is not. There are many warnings in Scripture that those who do not hold fast to Christ can be lost in the end (p. 23, prgh. 2).
Piper is correct in observing that there are many warnings in Scripture addressed to those who do not hold fast to Christ. Indeed, such people will be lost in the end. It is astounding, however, that Piper cannot see the glaring contradiction in what he says. Clearly, if a person is genuinely saved due to Gods unconditional election and irresistible grace, then there is no possibility of him losing his salvation. Thus, if election is unconditional, glorification must of necessity also be unconditional. If one is elected, he must by definition eventually be glorified. This very truth Piper has already declared one paragraph earlier:
It follows from what was just said [Pipers interpretation of Romans 8:28-33] that the people of God will persevere. The foreknown are predestined, the predestined are called, the called are justified, and the justified are glorified. No one is lost from this group. To belong to this people is to be eternally secure (p. 23, prgh. 1).
How can it be true that the elect will certainly be glorified and the elect may not be glorified? Both cant be true, yet Piper says otherwise! He blatantly contradicts himself in the space of a few sentences.
Moreover, logic dictates that if people are saved due to Gods unconditional election and irresistible grace, there is no sound reason for Scripture to warn anyone to persevere in faith. Those who are genuinely saved will persevere in faith and cannot do otherwise. They need no encouragement, because their salvation has been guaranteed since the foundation of the world. Likewise, those who are only phony believers have no reason to be encouraged, because their faith isnt genuine, and it is certain that they wont persevere, because their damnation has been guaranteed since the foundation of the world. To encourage such a person is to encourage him to remain deceived a little longer, until he discovers the inevitablehe has been predestined to be damned, and there is no reason for him to attempt to persevere in faith. His faith is bogus.
That is why it is virtually impossible for a consistent Calvinist to have absolute certainty of his salvation until his final breath, because he must always live with the fear that his faith may prove to be bogus if he doesnt persevere in faith until death.
Again, if unconditional election is true, conditional glorification cannot be true. If conditional glorification is true (which it is), unconditional election cannot be true. Yet Piper repeatedly maintains that both are true. For example, he writes:
We do not breathe easy after a person has prayed to receive Christ, as though we can be assured from our perspective that they are now beyond the reach of the evil one. There is a fight of faith to be fought. We must endure to the end in faith if we are to be saved (p. 23, prgh. 4).
Here Piper says that a person who has prayed to receive Christ is not beyond the reach of the evil one. But if that person is one of those who was predestined to be damned, he has not been truly saved in the first place and his prayer was ineffectual. He never escaped Satans clutches. If, on the other hand, the person is among those predestined to be saved, then there is no possibility of his forfeiting his salvation. And if he, being elected, is not beyond the reach of the evil one (as Piper says), then Satan is more powerful than God, and Piper has voided Gods sovereignty, something no good Calvinist should do!
A few paragraphs later, Piper reverses his position again, writing,
Gods elect cannot be lost. This is why we believe in eternal securitynamely, the eternal security of the elect. The implication is that God will so work that those whom he has chosen for eternal salvation will be enabled by him to persevere in faith to the end (p. 24, prgh. 7).
But if this is true, why are there so many scriptural warnings to believers against falling away from the faith, many of which Piper lists (e.g., Mark 13:13; 1 Cor. 15:1-2; Col. 1:21-23; 2 Tim. 2:11-12; Rev. 2:7, 10-11, 17, 25-26; 3:5, 11-12, 21)? If true believers cant fall away, why would Jesus and Paul warn them about what cant possibly happen?
The truth is, Scripture repeatedly warns believers against falling away because it is possible for genuine believers to fall away. For the same reason, Scripture also repeatedly admonishes believers to continue in the faith. All of such scriptures stand in direct contradiction to the Calvinistic doctrine of Perseverance of the Saints.
Piper then quotes from Jesus words in John 10:26-30 to prove that the elect cannot be lost. This passage of Scripture is the favorite of just about all who believe in eternal security, whether they are Calvinists or not:
But you do not believe, because you are not of My sheep. My sheep hear My voice, and I know them, and they follow Me; and I give eternal life to them, and they shall never perish; and no one shall snatch them out of My hand. My Father, who has given them to Me, is greater than all; and no one is able to snatch them out of the Father’s hand. I and the Father are one.
This passage of scripture, of course, is not the only passage of scripture in the Bible. It highlights the faithfulness of Christ, but notice that it also mentions some characteristics of those to whom Christ is faithful: Jesus sheep hear His voice and follow Him. They are the ones who shall never perish or be snatched out of His hand. This fits perfectly with the testimony of the rest of Scripture. As long as we continue in faith, as evidenced by our following Jesus, we need not fear that we will perish or be snatched out of our Fathers hand. If we stop following Jesus, we are no longer His sheep.
This scripture, like so many others, teaches a conditional eternal security. That is, we must continue to follow Jesus to ultimately be saved. Yet Piper uses this scripture to buttress his view of unconditional eternal security which stands in direct contradiction to his view of conditional glorification, which is nothing less than conditional eternal security! Piper believes in both unconditional eternal security (based on the doctrine of unconditional election) and conditional eternal security (based on the doctrine of conditional glorification). He is a very inconsistent Calvinist.
In this same chapter, Piper reverses his position again. Writing about believers who fall away, Piper says,
The fact that such a thing is possible [believers falling away] is precisely why the ministry of the Word in every local church must contain many admonitions to the church members to persevere in faith and not be entangled in those things which could possibly strangle them and result in their condemnation (p. 25, prgh. 3, emphasis added).
I couldnt agree more with that statement. But Piper again contradicts himself. After telling us that it is impossible for the elect to be lost, Piper now tells us that we must admonish church members to persevere in faith and not be entangled in those things which could result in their condemnation! But do these church members have a genuine faith? If yes, then they are among the elect and it is impossible for them to be ultimately condemned (according to Piper and all other Calvinists)! They need no admonishing. Or, is their faith bogus? If yes, then they are currently not saved and need no admonishing to continue in a faith that isnt genuine. They need to be saved, but will only be if they, according to Calvinism, have been unconditionally elected. And if they are not among those elect, then it is impossible for them not to be condemned (according to Piper and all other Calvinists)! We deceive such people even more if we encourage them to persevere in faith, because we give them a false hope that they are currently genuinely saved!
In summary, we see that the Calvinistic doctrine of the Perseverance of the Saints is, for the Calvinist, an absolutely necessary doctrine, even though it is unbiblical. If God bestows His irresistible grace on totally depraved people whom He has unconditionally elected, then it would have to be, of necessity, impossible for any of those people to forfeit the salvation that God gave them against their totally depraved wills. They are, of course, robots from start to finish. And it can be no other way in Calvins system of theology.
However, if people possess wills that are free enough to repent and believe under Gods prevenient grace, and if God has chosen from the foundation of the world to give eternal life to all who will believe, then it stands to reason that it is possible for regenerate people to fall away from faith by the exercise of their free wills, just as the New Testament repeatedly teaches. Because conditional glorification is indeed true, then unconditional election cannot be true. If there is an election (which there is) then it must be conditional. Thus the Calvinistic doctrine of Unconditional Election falls with the Calvinistic doctrine of Perseverance of the Saints.