The Scripture declares there are false converts. Only God knows with an absolute knowledge those who are His (born of God).
But that has nothing to do with the warning in the particular Scripture that
I just referenced, which was addressed to 'holy brethren' (ie False converts are NOT 'holy brethren)
The Scriptures are given to the church for instruction and discipleship. You know full well the church has unbelievers among us, thus, it is quite understandable that all of these warnings given to the church are for those believers and those unbelievers alike.
But the particular passage I quoted was not a warning to
false converts or those who were
already unbelievers. The warning was to 'Holy Brethren' (3:1), telling
them to beware lest there was in 'any of' THEM and evil heart of unbelief in DEPARTING from the living God (3:12).
False Converts
can't depart from the living God because they
were never with the Living God; nor were they
ever 'holy brethren' who had
never really believed to begin with!
Similar Scriptures could easily be given that have the same warning--that REAL believers can make shipwreck of their faith (i.e. believe in vain) and thus fall from grace [
can't fall from something you were never in!] as one is cut off from Christ [
can't be cut off from something you were never in!] in whom one was standing by faith (John 15:1-6; Rom 11:18-23, etc)
Could you please explain how you could stop believing in that which you have a personal knowledge of is an absolute truth?
Heb 3:13 which I quoted above shows one way. If one is not careful, one can be so hardened by the deceitfulness of sin that he departs from God in unbelief. By being hardened to the Holy Spirit (rather than repenting in response to His conviction), one's faith can die.
In the parable of the sower, Christ speaks of those who believe for a while (Luke 8:13), and who actually are said to have
something living which starts to grow the soil of their hearts, but whose soil is either (1) too shallow (never cultivated/deepened) and thus they fall away (Luke 8:13) and
lose faith* (Matt 13:21) when things get tough, or (2) is too cluttered with wordly things (that are never removed) that they ultimately
become unfruitful (Matt 13:22)
(
*Again, you can't LOSE something you never had, and Jesus does NOT say that this was a FALSE faith that they had lost!)
As I said above, I've read the testimony of atheists and agnostics who were at one time convinced that God was real and that Christianity was true. Yet, for whatever reason, either through continued unrepentant sin, or through the continued feeding of creeping intellectual doubts (rather than feeding faith), they stopped believing.