You were never a true Christian
"You were never a true Christian" is an accusation sometimes levelled at people who do not share the accusers own brand of Christianity or at people who abandon their faith. This is a way to avoid the problem of salvation supposedly being eternal.  By claiming a person was never a true believer in the first place, there is no contradiction. It also enables a believer of the "true" Christianity to claim that there is no disagreement among Christians (because people who disagree are clearly not Christian).
- "A person who rejects Christ and turns his back on faith is demonstrating that he never belonged to Christ. Those who belong to Christ remain with Christ. Those who renounce their faith never had it to begin with. "
- "Numerous atheists have claimed to have gone from being believers to unbelievers. It is difficult to confirm that these individuals were, in fact, true believers. Several atheists have written to me making such a claim. However, upon making further inquires of them, it has been clear that they never truly understood what faith meant, and never had any kind of experience with the Holy Spirit. So, I have never been able to confirm that a true believer has ever gone into unbelief. Even if they did, we would not know if they came back to faith later in their lives. "
- "Jonny, you never were truly a Christian and that is essentially your problem. [...] you have to attack a belief system you never truly understood in the first place. "
The claim is often supported by 1 John 2:19 :
- "They went out from us, but they were not of us; for if they had been of us, they would have continued with us. But they went out, that it might become plain that they all are not of us."
The accusation that someone is not a true Christian can be based on disagreements on obscure or overt doctrine. Both Protestants   and Catholics  have been accused of being non-Christian or not Christian "full sense of the word".
- "To consider heretics as Christians is not the teaching of the Church. "
No true Christian/Scotsman
- Main Article: No true Scotsman fallacy
This accusation is a classic "no true Scotsman" argument because it attempts to redefine ad-hoc what a Christian is, or what salvation requires.
According to their definition, no person is definitely a Christian because they may leave Christianity at some point in the future and were therefore never a Christian in the first place (It would be impossible using this criteria - the abandoning of a religion - to determine who, among current theists, is actually a "true theist"). How many unwitting imposters attend church every week? How come theistic fundamentalists were never able to "sniff these impostors out" while these "fakes" were still attending the same religious rituals as obediently as possible? This is clearly absurd. Not only that, but a Christian is, by objective definition, someone who believes in the Abrahamic deity and the crucifixion of that god's son, Jesus Christ, as atonement for an inherent sin of humanity. The definition of "Christian" says nothing about a person does in the future, such as doubting or abandoning the religion.
Apostasy is impossible
Since people who have "left" Christianity were allegedly never Christian in the first place, the sin of apostasy is impossible. Allegedly, there were always a non-believer!
Understanding requires belief?
Since many Christians believe that without salvation, Christianity cannot be truly understood. Therefore, anyone who disagrees is not a Christian and is simply incapable of understanding.  In other words, you either always follow these people (but not other theists who interpret scriptures differently) without questioning nor reasoning, OR you never were a "real theist" to begin with, you were always a lost cause unable to grasp the divine message of their religion; otherwise, you supposedly would have never dared considering the possibility of something being wrong (morally or factually) with the whole picture. This allows any criticism of fundamentalist beliefs to be safely ignored.
- ↑ 1.0 1.1 Rich Deem, Security of the Believer: Once Saved Always Saved?, Last Modified January 6, 2012
- ↑ 
- ↑ AislingNB (@AislingNb), June 18, 2013 at 5:22 pm, comment on Leaving Fundamentalism blog 
- ↑ 
- ↑ 5.0 5.1 
- ↑ 
- ↑ Jonny Scaramanga, You were never a true Christian, Leaving Fundamentalism blog