The truth is--situations like the one described above are not that uncommon. In fact, my personal story follows a similar plot line. I expressed interest in salvation as a five-year old boy (even to the point of "making a decision") and operated under the assumption that I was saved until I was 14. It was at that point that I understood the Gospel truths (for the first time, really) and was saved. Doubtless, there are others who have grown up in church or have attended church for many years who could give similar testimony. I have even heard stories of visiting evangelists coming to a church, preaching rather forcefully, and seeing dozens of church members (including deacons and other leaders) saved as a result.
This concept of "Unsaved Christians" (that is--those who claim to be and even believe themselves to be saved but may or may not be) is an intriguing one to me. What are we to make of scenarios like the ones I have already mentioned? Obviously, if someone has been deceiving others and/or themselves about their spiritual condition, then I rejoice with them in the fact that they are now justified before God. If someone thought they were saved but were not because they did not truly understand the facts of salvation (as was the case in my life), their salvation decision is most assuredly a wonderful thing.
On the other hand, what if a person was not confused? What if they were not living a lie? What if they were truly, genuinely saved before they "got saved" (the most recent time)? What if, beforehand, they understood the Gospel, had already "made a decision", and believed themselves to be a child of God? What are we to make of a situation like that?
As you might have guessed, I have several thoughts on this subject.
The first question I would ask someone in this situation is this, "What was it that brought you to the conclusion that you weren't really saved all this time?" Their answer to this question is critical. If their answer indicates that they did not understand or believe the Gospel truths, then I say, "Praise God! You are now a Christian!" However, I believe there is cause for concern if they answer something along these lines--"Well, I thought I was saved, but when I heard that message tonight, I just knew I needed to 'really' get saved!" or "Well, I thought I was saved, but I haven't really been acting like it much in my life, so I realized I needed to 'really' become a Christian." In my opinion, conversion decisions for "Unsaved Christians" based upon fear-inducing preaching or a lack of "fruit" in one's life are built upon a shaky foundation, and I will explain why as quickly as I can.
Although the Gospel deals in part with fearful concepts (hell, death, eternity, punishment, etc...), I question the wisdom of using fear as our primary means of persuading people to be saved--especially when dealing with a group of people who already think they are saved. The truth is, this is the preferred M.O. of many a preacher and evangelist, and it does produce results, but...I am still uncomfortable with this philosophy. Is it really a healthy habit to scare Christians into "really" getting saved? "What if they aren't Christians?" someone might argue, "What if they really do need to be saved? Shouldn't a preacher present the Gospel as powerfully as possible in order to convince the lost to accept Christ?" My answer to that line of argument is this. If someone is not saved, the thing that needs to bring them to a point of conversion is the true drawing and conviction of the Holy Spirit of God not fear and intimidation. If someone is saved, the last thing I want to do is convince them that they are not. Many evangelistic sermons do that very thing, and cause a great deal of confusion and doubt in the process. There is a fine-line between powerful preaching and "fear-mongering", and it seems to me that the negative consequences of the latter should cause many preachers to adjust their approach. Don't forget, the Gospel is, at its core, "good news."
In the situation of someone getting saved because of a lack of evidence in their lives, I also have reservations. (Coincidentally, many of the fear-inducing sermons mentioned in the previous paragraph use this "lack of fruit" idea as the basis of their Gospel appeal.) I know that the conventional wisdom in many Christian circles stipulates that those who are "truly" saved will, inevitably, demonstrate this in their lives, but I don't buy it. The New Testament is replete with examples of individuals who were saved but did not act like it. (Have you read I Corinthians lately?) Many of the New Testament Epistles were written to convince those who were already saved to act accordingly (Ephesians 4:1). Does this not imply the possibility that a Christian can be a true Christian but act in a very un-Christian way? To resolve the problem of carnal Christianity by simply declaring one's salvation to be invalid and basically starting over is, in my mind, a lazy and faithless approach. It's the equivalent of a "mulligan" in a round of golf. This term refers to a golfer taking a "do-over" when they aren't doing particularly well on a hole. It's not officially a part of the rules, and true golfing purists aren't likely to advocate the use of "mulligans". Part of playing the game of golf is to play the ball where it lies, no matter how difficult it might be. The fact is, the Christian life is one of constant contradictions--victories and defeats, ups and downs, growth and backsliding, progression and regression. The solution for a defeated Christian is not to take a "mulligan" and start over, thinking that somehow it will be different this time. The solution is to "play it where it lies"--to come to God as a Christian, admit your weakness, and implore Him for His help. This is a request God is more than willing to grant.
The biggest problem with these scenarios that I have mentioned is that the individual's assurance of salvation is based on shaky ground--feelings and actions--when it should be based on the unchanging, unwavering truth of God's Word concerning salvation. That is why I am a bit wary when I hear of "Unsaved Christians" getting saved.
For what it's worth...