The one question Conditional Security believers have to answer is if you can lose salvation, how? The only answer they will ever be able to give is "by falling away". This, I can level with. Based on 1 John 2:19 and other passages, I contend a true Christian won't fall away, but at least this reasoning fits in with salvation by grace through faith and not of works (Ephesians 2:8-10). Therefore, it's a fair answer. But no other answer is sufficient. If we are saved by grace through faith, apart from works, then we must logically retain that salvation in the same manner. After all, having begun in the Spirit, shall we be perfected by the flesh? (Galatians 3:3).
It is ironic that proponents of Conditional Security, much like proponents of works based Gospels, argue that Eternal Security downplays sin. If we can both receive and retain salvation regardless of works, why don't we? The simple answer from an Eternal Security standpoint is because we are saved. You can be a bad spouse and remain married, the problem is you're a bad spouse, which if you love your spouse, why would you want to? You can be a bad Christian and remain saved, the problem is you're a bad Christian. If you love God, wouldn't you want to be a good Christian?
Conditional Security, in theory, can produce the same attitude. But we all sin, regardless of how confident we are that we have eternal life. The problem is, the sins we commit now are the same sins we would have gone to Hell for were it not for the cross. Are they somehow no big deal after the cross? You lie before the cross, you go to Hell. You lie after the cross, eh, it's just a lie. Jesus can forgive that.
How is this not downplaying sin? If you believe you can lose salvation through sin, you must inevitably downplay your own sin. Otherwise, you would have to contend that a grand total of 0 Christians retain salvation for much longer than 5 minutes. Run your mind through the past hour. Have you not sinned? And that's just one hour. How long have you been saved? If you believe in Conditional Security, you may well say just one hour. But let's be honest, that's just not realistic, and you certainly can no longer say you believe salvation is by grace through faith and not of works. But if you go by how long you've professed faith in Jesus, you've sinned endlessly. Yet, presumably, you consider none of those sins sufficient to lose salvation.
Conditional Security provides a grand total of two logical options: 1. You are not saved, because sin is so severe you should go to Hell. 2. You are saved, but sin becomes less of a problem after salvation. Both of these options are repugnant. It is Christ who saves, and therefore though sin is great in severity, salvation is greater. Conditional Security is a lie. It borders on a false, works-based gospel. The only reason I can say borders is because not all who profess it hold to works-based gospels. They still claim salvation is by grace through faith and not of works. But think about it, if salvation could be lost, it would have to be by works. The only exception would be by falling away from the faith. Beyond that, you are effectively saying we are saved by grace through faith and works. That, my brethren, is heresy.