Salvation Stands

1 Corinthians 15:2 KJV

By which also ye are saved, if ye keep in memory what I preached unto you, unless ye have believed in vain.

Salvation stands upon the Gospel of Jesus Christ, a gospel Paul was about to reiterate, with two provisions:

If you keep in memory what I preached unto you.

The whole of the Bible teaches that our eternal destiny is not based upon our ability or inability to remember particular messages of even specific doctrines. A case can, I believe, be made for the doctrine of perseverance. A true believer will be a believer to the end. A genuine Christian, though human and easily swayed, will swing back always to faith in Christ. His body and mind may, for a time, be pulled away from his convictions but the Holy Spirit, who inhabits every true Christian, will direct the back to Christ.

I think rather we ought to read this as a statement of fact rather than a question. The point is that they had remembered the gospel that had been preached unto them. Though they had been tested, though false apostles had attempted to draw them away, these believers were believers still. They of course needed instruction, but they willingly received that instruction. They had remembered what Paul preached to them.

Unless you have believed in vain.

Which is an impossibility. No true believer can believe in vain because what he believes is not vanity.

The rest of this chapter will be dedicated to bearing that fact out.