In recent days there has been news of a former mega Church leader and author who has decided to walk away from Christianity. Consequently, some Christians have taken the position that this person was never a believer to begin with, and base their conclusion on a scripture from 1 John, which says the following:
They went out from us, but they were not of us; for if they had been of us, they would no doubt have continued with us: but they went out, that they might be made manifest that they were not all of us. ~ 1 John 2:19
The problem with this conclusion is that John is not referring to those who turn away from the faith because of deception, offense, unresolved questions, etc.
John is referring to seducers who are false teachers, false prophets, and even false brethren, who have an anti-Christ spirit. At first they may appear to be true ministers and brethren, but eventually who they truly are comes to light through their message and works which are contrary to Christ.
Below is 1 John 2:19 in context:.
Little children, it is the last time: and as ye have heard that antichrist shall come, even now are there many antichrists; whereby we know that it is the last time. They (the many antichrists) went out from us, but they were not of us; for if they had been of us, they would no doubt have continued with us: but they went out, that they might be made manifest that they were not all of us. But ye have an unction from the Holy One, and ye know all things. I have not written unto you because ye know not the truth, but because ye know it, and that no lie is of the truth. Who is a liar but he that denieth that Jesus is the Christ? He is antichrist, that denieth the Father and the Son. Whosoever denieth the Son, the same hath not the Father: he that acknowledgeth the Son hath the Father also. Let that therefore abide in you, which ye have heard from the beginning. If that which ye have heard from the beginning shall remain in you, ye also shall continue in the Son, and in the Father. And this is the promise that he hath promised us, even eternal life. These things have I written unto you concerning them that seduce you. ~ 1 John 2:18-18