All the elect endure to the end by Gods grace. Only true believers are the elect in Christ. What you speak of are tares among the wheat (true believers). Pretenders and false professors are apostates and tares among the visible church. And warnings in scripture are to encourage true believers of their leaven and to call to repentance these tares. 1 John 2:19 is obvious that they were NEVER among the elect in Christ. Because if they had been they would’ve remained in the faith. But they were made manifest to the church that they were imposters. Only a tare would take the mark. By promoting loss of salvation, you therefore promote that your works maintains your salvation. There’s no Christ nor gospel in this false teaching
You have committed a logical fallacy otherwise popularly known as an overgeneralization. Just because SOME believers who depart from the faith were never saved to begin with, it does not logically entail that ALL believers who depart from the faith were never saved to begin with. Do you believe that just because SOME chickens lay brown eggs, therefore ALL chickens must lay brown eggs? Yes or no? This shows the logical weakness of your held conclusion. Furthermore, you have neglected to explain how it is possible for an unbeliever who never had faith to begin with, to apostatize and fall away from the faith that he/she never possessed. It is impossible for an unsaved person to apostatize. Thus Scripture is replete with warnings to the believer against apostatizing.
You have also managed to avoid answering my simple question which directly contradicts with your held view of OSAS. I have proposed this same scenario to others who share your belief and the result is always the same. They avoid answering my simple question or they answer in terms of what someone else might do. Thus, I'll lay it out for you and you can choose to respond or not respond as that is your prerogative.
If Jesus does not return before the great tribulation and you find yourself in the position of having to decide whether or not to take the mark of the beast, would YOU take the mark?
As far as I know, YOU have 3 possible options:
1. Yes, take the mark because I’m eternally secure. This response indicates that you are at least consistent in your belief. However I’ve found no one responding in this manner because they know that this affirmative response directly contradicts the plain warning given in Rev 14:9-11.
2. No, don’t take the mark because if I do it would demonstrate that I was never a believer/elect to begin with (which your stated claim based on 1 Jn 2:19). This option puts to rest your notion that those who continue to sin or no longer believe and depart were never believers in the first place. I have no reason to doubt you are saved; yet at the same time you would have acknowledge the consequence of you losing your salvation upon taking the mark. It puts you in a quandary because according to your belief, if you took that mark it would mean that you are a tare/unbeliever who was never saved - which I presume you have a hard time accepting. You can no longer use the excuse that persons who fall away from the faith never really believed.
3. No, don’t take the mark because if I do I’m condemned to the lake of fire. If this option is taken, a person who adheres to eternal security acknowledges that the warning of taking the mark applies to him/her personally and the doctrine of eternal security is no longer a valid belief.
A person who believes in the pre-trib rapture might protest and claim that this is not valid and is only a hypothetical example since the church is raptured before the great tribulation. However Rev 14:12 notes that the saints are still present at the time when the mark is presented. Whether this is the entire church or only tribulation saints is another matter for discussion. The main point is that v.12 commands the
saints to persevere and be patient by keeping God’s commandments and their faith. Taking the mark would demonstrate that a saint has not kept the commandments and his/her faith.
Finally, I have had people avoid answering my question by replying that under no circumstances would they ever take the mark. I ask them how can they be so certain of what they will do, or not do in the future - especially under extreme duress? I state that for myself, the most I can say is that I hope with God's grace I will refuse to mark. They reply by saying that they just KNOW they will not accept it. I then remind them that Peter was also certain and self-assured when he boldly proclaimed that he would never deny Jesus, and we both know what happened to Peter afterwards. Peter's example is an example for us. Of course later on, Peter was repentant and forgiven however his presumption of always following Christ is a warning for us not to be so self-assured of ourselves.