historically, 1John was written to address the issues in the Ephesian congregation and one of them was the denial ( by those in the congregation) that Christ had indeed come in the flesh ( incarnate) or that he even existed at all (outside the congregation). There were issues that Christ was never really Man and some thought that His ressurected body was NOT flesh and bone, but spirit only.
Yes, I understand that that is what is taught as to what John wrote and why, dear one (again, peace to you!)... perhaps what some even thought he was addressing. But I am not so sure, based on the entire book, and particularly the preceding/succeeding verses:
"Beloved ones, do not believe every inspired expression, but test the inspired expressions to see whether they originate with God, because many false prophets have gone forth into the world. Y OU gain the knowledge of the inspired expression from God by this: every inspired expression that confesses [Jesus] Christ as having come in the flesh originates with God,..."
In other words, YOU gain the knowledge that the inspired expression was from God... by means of its confession of Christ in YOU. This is what Paul meant when he wrote:
"The spirit itself bears witness with our spirit..."
HOLY spirit, then... which is IN us... is what "bears witness" to whether the inspired expression came from God. If one does NOT profess that spirit, however, then the expression did NOT originate with God. And only those who HAVE such spirit... can profess that it is IN them. Hence:
"... every inspired expression that does not confess [Jesus] does not originate with God."
Meaning, every inspired expression that does not confess Christ AS THE SOURCE... does not originate with God. It CANNOT. Thus, it is:
"... the antichrist’s [inspired expression] which YOU have heard was coming, and now it is already in the world."
That "spirit"... is the spirit that DENIES Christ... his spirit... IN the Body... the people... by means of denying his and its indwelling IN people, literally. Which is what these false prophets were doing.
John explains, when he writes:
"Y OU originate with God, little children, and YOU have conquered those [persons], because he that is in union with YOU is greater than he that is in union with the world. They originate with the world; that is why they speak [what proceeds] from the world..,"
Because the spirit of GOD is not IN them... because CHRIST is not in them.
John was adressing these issues ( and others of course), hence his waring against the false prophets and what they were professsing.
It appears, from a reading of the entire letter, that John was addressing the lack of love shown by those who WEREN'T of the Body, but who PROFESSED to be, and so were persecuting those who WERE... by going around teaching falsehoods such as (1) the Christ didn't dwell IN people and perhaps Jah eShua even the Christ, that even so, Christ does/did NOT occupy his Body by means of spirit prior to his return... but would only be "with" them when he returned... in the spirit. John wasy saying that these had "gone out from among them"... because they were never really a PART of them... because they did not profess an occupation/union with/by means of holy spirit but actually DENIED that occupation/union.
By means of this, the congregation was being disrupted and some were being misled, especially into doubting who they were and what they knew. Which is why John admonished them as to those trying to mislead them and REMINDED them that they DID know... that it was the very anointing (occupation) that was teaching them... and so they didn't NEED others to teach them as to these things (who and what they were... why... and by what means). They KNEW... because the spirit IN them TOLD them.
Again, I understand the "historical" direction you were coming from. But I would ask you to go to our Lord and ask HIM if that "history" is accurate. I don't believe, after hearing HIM on the matter, that it is.
Again, peace to you, dear one... and, as always, no intent to contend, but to just share the truth. Which I know doesn't always jibe with "history."
Your servant, sister, and fellow slave of Christ,
SA