A number of commenters on Atheist Central used to be Christians and de-converted to become atheists. So the question often comes up whether they were real Christians. Can a real Christian lose his or her salvation? And what is a real Christian?
The Bible uses the word "elect" to describe real Christians, but although this involves being chosen and redeemed, it doesn't necessarily imply determinism. So I will sidestep the perennial debate between Calvinists and Arminians and simply say that God who sees to the end of time and throughout all eternity knows exactly who they are. He has always known who they are, even before he created the world. So of course the elect cannot lose their salvation. That would be a logical impossibility, because if they do they would not be among the elect. 1 John 2:19 says: "They went out from us, but they were not really of us; for if they had been of us, they would have remained with us." Anyone who leaves the faith permanently is by definition not one of the elect.
However, those of us who are living out our lives in space-time still have to "overcome," according to Revelation 2:7. Matthew 24:12-13 says: "Because lawlessness is increased, most people's love will grow cold. But the one who endures to the end, he will be saved." So most people will not finish the race, and the evidence of that is simply love that has gone cold. No de-conversion is necessary. This makes sense, because Matthew 25 tells us that Jesus will judge us based on our acts of love or their absence.
Does this mean that those who "shipwreck" their faith were never truly converted? Although that is the modern conventional wisdom, I don't think it's biblical, and this is why: In 1 Corinthians 9:27, Paul says: "I discipline my body and make it my slave, so that, after I have preached to others, I myself will not be disqualified." So Paul himself was not completely sure that he would finish the race. If he had not finished, it is true that he would not have been one of the elect, but would his conversion have been real? Well, how many of us saw a flashing light, heard an audible voice, and were struck blind only to have the "scales" physically removed from our eyes upon conversion? And if that's too subjective, he had independent confirmation. Ananias heard an audible voice telling him that Paul was God's chosen instrument. So it is possible to have a real conversion and fall away.
However, although Paul considered apostasy a possibility, he had complete faith in God that he would bring him "safely to his heavenly kingdom" (2 Timothy 4:18). He expressed the same faith in God's work in the lives of the Philippians, saying, "For I am confident of this very thing, that He who began a good work in you will perfect it until the day of Jesus Christ" (Philippians 1:6). But if we read the context, we see that the Philippian church was thriving and bearing much fruit, so Paul's confidence was well-founded.
The Galatians were a different matter, because they had allowed a spirit of legalism to take root, and it is the most deadly and soul-destroying. We know that they were originally true converts because Paul says: "Did you receive the Spirit by the works of the law, or by hearing with faith? Are you so foolish? Having begun by the Spirit, are you now being perfected by the flesh?" (Galatians 3:2-3). They had begun in the Spirit. And yet in verse 4 Paul expresses fear that it would all be in vain. Galatians 1:6 says, "I am amazed that you are so quickly deserting Him who called you by the grace of Christ, for a different gospel; which is really not another." They were on their way to apostasy, and it is no wonder because legalism cannot produce the fruit of the Spirit, and therefore love would be absent. Paul uses strong words like "foolish" and "accursed" in this letter because their danger was so great. Compare that to the affection with which he addresses the Philippians.
The parable of Luke 13:6-9 illustrates this issue of Christians who do not bear fruit: "A man had a fig tree which had been planted in his vineyard; and he came looking for fruit on it and did not find any. And he said to the vineyard-keeper, 'Behold, for three years I have come looking for fruit on this fig tree without finding any. Cut it down! Why does it even use up the ground? And he answered and said to him, 'Let it alone, sir, for this year too, until I dig around it and put in fertilizer; and if it bears fruit next year, fine; but if not, cut it down."
We have an immediate hint that there is something amiss: What is a fig tree doing in a vineyard? Fig leaves represent dead works in the beginning of Genesis, where Adam and Eve cover themselves with fig leaves after the fall. And Jesus curses a fig tree when he sees only leaves and no fruit. So we suspect that this fig tree in the parable represents a Christian who will not ultimately prove to be one of the elect. But in the parable, Jesus, the "vineyard-keeper," doesn't give up. He does whatever possible to encourage growth. However, in spite of all his efforts, apostasy may be the end result. That is represented by the words, "cut it down." It is no longer part of the vineyard, or the living church of Christ.
So what does this mean for us? If you are an ex-Christian atheist, your conversion may have been every bit as real as it seemed to you at the time. And you may have abandoned your faith because of intellectual questions that were never answered. There is no reason to conclude otherwise. However, as the parables of the lost sheep and the lost coin illustrate, Christ is always seeking to bring you back.
And as Christians, we have to distinguish between complacency and faith. Philippians 2:12-13 says, "Work out your salvation with fear and trembling, for it is God who is at work in you both to will and to act according to His good pleasure." "Fear and trembling" means "no complacency." It's very easy to conclude that there are a lot of false Christians out there, but we couldn't possibly be one of them. If we believe that many will be told "I never knew you" on the day of judgment, it logically follows that we could be among them. We need to ask ourselves honestly whether Paul would use the same words with us as he did with the Galatians.
However, if we feel convicted, that is always a sign that God is at work within us, bringing us to repentance. It means we are not hardened. And true repentance always leads to surrender and trust in Christ, letting him do the good work within us. We can't possibly fix ourselves by deciding to behave better next time. What is in us will always come out, and Jesus deals with what is in us.
This reminds me of our youngest son's solution to the problem of strawberry seeds that were not growing (in the interest of full disclosure, I think we had been forgetting to water). He simply attached some nice ripe strawberries to a couple of chopsticks, stuck them in the planter, and voila! we were "growing" strawberries. However, those strawberries were not receiving nourishment and therefore wouldn't last very long.
We cannot produce good fruit without staying close to Christ. We are only called to abide in him like a branch on a vine, and he will by his Spirit produce within us the fruit of love, joy, peace, patience, goodness, kindness, gentleness, faithfulness, and self-control (Galatians 5:22).
And he alone is able to keep us from stumbling and make us stand in the presence of his glory blameless with great joy (Jude 1:24).