James Jordan’s reading of 1 John 2:19:—
“Out from us they went out,” — that is, they set out on teaching missions.
“But they were not out from us,” — that is, they had no valid commission from us.
“For if they were out from us they would have remained with us,” — that is, if they had valid commissions from us, they would have remained with us in our true teaching.
“But [this happened] in order that they might be manifest that none of them are out from us.” — that is, their false teaching shows that they were not sent by us.
This seems to me to make far more sense of 1 John 2:19 in its context than those readings that take the verse as working in terms of a visible/invisible Church distinction. This verse is currently being discussed on Lane Keister’s blog.