NOTES for Jo2 1:8
What does the apostle mean when he calls his fellow believers to "watch themselves" so as not to lose the promised reward? What loss is being spoken of? And what exactly must be watched so that everything will be in order?
Judging by the context of the statement, one can think that the matter concerns doctrine, orthodoxy, which must be preserved, otherwise there is a risk of losing the Kingdom, and with it salvation. At first glance, such a call is quite natural: representatives of every religious teaching, and indeed of any other teaching, are always to one degree or another concerned about the purity of their own ranks, including purity, so to speak, of worldview. After all, any religious community needs adherents capable of spreading the teaching and attracting new members. But Christianity is not a religion; it is life in the Kingdom brought into the world by the Savior. To be its inhabitant, one needs faithfulness not to an idea, not to a doctrine, and not to a creed, but to God and Christ, to the Torah and the Gospel. This is a question not so much of views as of practical life, not so much of orthodoxy as of orthopraxy.
But then what do questions of right belief have to do with it? Can they influence that very life in the Kingdom which constitutes the essence of Christianity? It is obvious that if such influence is possible, then only in one aspect: in the aspect of the relationships that bind an inhabitant of the Kingdom with God, with Christ, and with neighbors. A person's relationships with God and neighbors are exhaustively described and regulated by the Torah; the Decalogue is sufficient for them. But relationships with Jesus depend in many respects on whom the person approaching Him sees in Him. Jesus' question, "Who do people say that I am? And who do you say that I am?" is addressed, in essence, to each of us. And one must answer it every time one wants to share a meal with Him during the breaking of bread in the church assembly.
Apparently, already in John's time there were many gnostics in and around the Church for whom Jesus was never a Man, who were ready to see in Him rather an angel or some higher spirit. The spiritual danger here lay not in wrong belief as such, but in the fact that such a view of Jesus made transformation impossible for a person, and therefore participation in the Kingdom impossible, at least in this life. Then both the breaking of bread and the very existence of the Church lost their meaning: after all, according to another apostle's definition, she could in no way be the "body of Christ" in such a case, and in any other capacity she could give a person nothing that the Synagogue could not give him.
Orthodoxy was never needed by the Church in itself; in itself it could be needed only by church structures parasitizing on her. For the Church herself, in fact, it was always necessary only from the point of view of the main question Jesus once asked the apostles: who do you say that I am? Because the very possibility of life in the Kingdom depends on the answer to it. And therefore so does the possibility of salvation.