Amen to this one as well.........!
I likewise agree that we do receive encouragement of the scripture concerning becoming the children of God. And we also have the written witness concerning how we can know (in us) by the other (Who moved to former to write, but is as He that continues to write), but in us (even though them)
Even in this its like two witnesses (one, in the record of written word of the Word) our belief in the truth (that God sent His Son) and the living Spirit that abides and writes upon us if so be He dwells in us.
Its amazing to think on, like one testimony speaks (even if through written witness accounts) which account of many lives (living through the testimony of Him) unto the confirmation of the same (which would bear witness within us)
Did I even put that right? I hate putting the things I think on in these things in my own words so much because they can often fail us.
However, I do think thats rather beautiful, just how something is known to us by the living Spirit (in us) and not only what is written in ink, and yet it is confirmed in ink. And how (in real time) how we are to become an living epistle ourselves to be known and read by all (not written in with ink) but the Spirit of the living God.
Because even though we (intimately) might know by the same, so also are the children of God (even the children of the devil) manifested. So written witness, inner witness and know and read by others, would agree in that they are manifested even as 1 John speaks of the same.
God richly bless you in Christ Jesus the Lord