I personally believe the bible is VERY CLEAR that salvation can be lost.
Hebrews 6:
4For it is impossible for those who were once enlightened, and have tasted of the heavenly gift, and were made partakers of the Holy Ghost,
5And have tasted the good word of God, and the powers of the world to come,
6If they shall fall away, to renew them again unto repentance; seeing they crucify to themselves the Son of God afresh, and put him to an open shame.
The people these verses are speaking of were not "most likely not saved in the first place". They were partakers of the Holy Ghost. You cannot partake of the Holy Ghost if you are not saved.
Hebrews 10:
26For if we sin wilfully after that we have received the knowledge of the truth, there remaineth no more sacrifice for sins,
27But a certain fearful looking for of judgment and fiery indignation, which shall devour the adversaries.
28He that despised Moses' law died without mercy under two or three witnesses:
29Of how much sorer punishment, suppose ye, shall he be thought worthy, who hath trodden under foot the Son of God, and hath counted the blood of the covenant, wherewith he was sanctified, an unholy thing, and hath done despite unto the Spirit of grace?
30For we know him that hath said, Vengeance belongeth unto me, I will recompense, saith the Lord. And again, The Lord shall judge his people.
31It is a fearful thing to fall into the hands of the living God.
These people have RECEIVED knowledge of the truth. And notice it says, "wherewith he was sanctified" which means this person was definitely saved to begin with.
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Colossians 1:
21And you, that were sometime alienated and enemies in your mind by wicked works, yet now hath he reconciled
22In the body of his flesh through death, to present you holy and unblameable and unreproveable in his sight:
23If ye continue in the faith grounded and settled, and be not moved away from the hope of the gospel, which ye have heard
Notice the "IF"
There are many other examples, but I'm too tired to come up with them now. Will post more later.