NOTES for Jo1 1:1-4
In bearing witness to Christ, John at the same time bears witness to the Kingdom. It cannot be otherwise: they are inseparable. The very appearing of the Son is connected with the fact that God's life, the life of the heavenly Father, formerly invisible and unreachable, becomes visible (v. 2). Visible through a concrete Man and in a concrete Man, whom one can touch with one's hands and examine just as we can examine and touch everything that exists in our world (v. 1). And through this, one can become part of the Kingdom, share in the life by which the Father lives and which the Son bears in Himself in all its fullness (v. 3). This is Christianity. John does not speak by chance of the fullness of joy (v. 4; the Synodal translation calls it "perfect joy"). The point is that joy which is connected with God's presence in the life of a person or a community. This joy, of course, was known even before the coming of Christ.
But no one in pre-Christian times knew its fullness. And the issue here is not that it was never experienced in fullness by anyone, nor even that every joy, together with life, then ended in Sheol, the world of shadows, the kingdom of the dead, which made everyone equal. The issue is that the breath of God, the breath of the Kingdom, could not be contained in fullness in any human heart - and therefore could not be revealed to the world from within, so as to be accessible to every seeker.
From outside, this breath reached people, and in the world at all times there were people who sensed it. But to transform our world completely, to return it to the state in which it could again become part of the Kingdom, as it was before the fall, can be done only from within. And the Savior, coming into the world, brings the Kingdom into it. In all the fullness now accessible to every seeker who is ready to trust Him.
But to share in the life of the Kingdom means not only to touch it outwardly. It also means to let it in. To make our heart become the door through which the breath of the Kingdom enters the world. This is beyond the strength of fallen man. But one can open one's heart to Christ, let Him into one's life, and then He will make our heart the door through which the breath of the Kingdom will burst into the world just as it once burst into it through the open windows of the upper room in Zion. Then our life will become Christian to the end - we will live by the Kingdom and in the Kingdom.