Agreed.
John was very worried about gnosticism invading the church.
When he writes: They left us because they were not of us...
He was speaking about gnostics that realized they did not belong to the church.
What you say about the gnostics is correct, of course.
I'm not insisting that John was NOT speaking about gnostics because some theologians believe he was.
And it does make logical sense also.
But then what does
1 John 2:1 mean?
1My little children, I am writing these things to you so that you may not sin. And if anyone sins, we have an Advocate with the Father, Jesus Christ the righteous;
John is addressing MY LITTLE CHILDREN....
He is writing so that they may NOT sin...
BUT IF anyone sins, we have an advocate with the Father...
This is for Christians.
It would seem to me that John knows that some will still sin,
but we can confess our sins to God Father.
Also, after I read your "Edit" I'd like to get into some history...
1 Corinthians 3:14-15 is used by Catholics to support their doctrine of purgatory.
Actually, it's speaking of the ministry of Paul and Apollos.
You used the same verse I did...SO THAT YOU MAY NOT SIN...
But then John gives these Children of his a way out...
Why?
Here's the history I'd like to share with you, seeing as how you know and enjoy history (I think).
The Catholic Church does actual confession - confessing to a priest who announces the penitent to be forgiven by God.
Confession was not always practiced as it is today.
At the beginning persons confessed audibly in a group, in a "church" setting...be it a bldg or a home.
This caused problems, as you can imagine. So it changed, gradually, to what they do today.
But WHY have confession at all?
At the beginning it was believed that those that were believers and were baptized would automatically stop sinning.
It was realized, very quickly, that even those that were baptized - thus being buried and risen with Christ - would still be sinning
at some point or other; even though their life changed for the better.
So how could this be handled?
Since Jesus told the Apostles in John 20:23 that they could forgive or retain forgiveness for sins, they decided on some type of communal
confession for forgiveness of sins.
Let's leave it at this for now.
But do you know what the ECFs thought about sinning?
Maybe next time...