A man named John was sent from God.
He came for testimony, to testify to the light,
so that all might believe through him.
John the Baptist and the author of First John seemed to share in common a humility before the truth of the message they proclaimed. The Baptist was not the light came to testify to it, saying of Jesus that, "The one who is coming after me ranks ahead of me because he existed before me". The author of First John did not write as though he were in special possession of of the truth that only he could convey, or that he had enticing secret knowledge to offer. He did not in fact write to give his audience anything that was uniquely his, but rather to remind them of what was already their own.
I write to you not because you do not know the truth
but because you do, and because every lie is alien to the truth.
This, we might assume, was in contrast to the antichrists that went forth from the early Church. They deserted her both in terms of affiliation and of doctrine. They could only survive by parasitically promoting what was uniquely their own, their own doctrinal spin. They could make the case that they possessed something unique that would set their adherents apart as insiders, better than those who merely knew what everyone in the Church was taught to know. But John wrote to assure his audience that they didn't need the novelties taught by antichrists. At a fundamental level they already had what they needed, and it was not something that could come from merely human teaching.
But you have the anointing that comes from the Holy One,
and you all have knowledge.
They had been given the gift of the Holy Spirit, and with him all of the gifts that he conveyed. He was "the Spirit of wisdom and understanding, the Spirit of counsel and might, the Spirit of knowledge and the fear of the LORD" (see Isaiah 11:2) and he brought these gifts to all in whom he receive him. The Holy Spirit would provide the early Christians the assistance they needed to hold fast to the truth they had received even in the face of subtle distortions and perversions of that truth. And the Spirit continues to do so even in our own day, no matter how confusing things seem to become. He helps us to remain faithful to what we have received from the beginning, the core doctrines of our faith. Without him we might be easily unsettled by things that were said by this or that theologian, priest, or bishop. But with the Spirit we are kept safely within the body of Christ and will not follow those who go off on their own and try to lead away the sheep to follow them (see John 10:5). The Spirit may not make us competent to write theology papers, or even biblical reflections that are perfectly free from error. But he absolutely does help us reject what is contrary to the faith. This means that we ought not rely only on our intellect alone or only on the preaching of good preachers, but should rely on the supernatural gift we already possess.
But to those who did accept him
he gave power to become children of God,
to those who believe in his name,
who were born not by natural generation
nor by human choice nor by a man’s decision
but of God.
We are meant to walk in a reality that is deeper and more comprehensive than anything an antichrist could offer. They taught lies and distortions. But Christians are invited to something that is more than merely intellectual. We are in fact made sons of daughters of God by faith, and as a result we are given to share in God's own Spirit. We no longer need to struggle as isolated individuals trying to figure everything out on our own. We can instead lean on and trust what God himself has taught us. If we remain open to the gift we have been given the Spirit can guide us through the voice of conscience helping us to approve the truth and reject its many counterfeits.
And the Word became flesh
and made his dwelling among us,
and we saw his glory,
the glory as of the Father’s only-begotten Son,
full of grace and truth.
As lay faithful we may not be able to articulate every doctrine of the incarnation, the natures and the person of Christ. But we have a sense that is trained and ready to reject the many lies that have been told about it. Antichrists have said that Jesus only appeared human, or that he was some great being, but less than the Father, or that the stories about him were only true in some vague poetic sense. Such lies dissolve in the fire of the Spirit we have been given. He moves us from within to reject them as alien to the truth.
From his fullness we have all received,
grace in place of grace,
because while the law was given through Moses,
grace and truth came through Jesus Christ.
What we have received in Christ cannot be explained by simply calling it the prejudice of long familiarity. The Spirit is alive and vibrantly helping us to proclaim, "Jesus Christ is Lord!", in a way no mere aggregation of teaching and emotion could ever truly emulate.
The fact that we have been given this anointing and have all knowledge does not mean that we can rest on our laurels. It rather means that we should be eager to delve deeper into the mystery of Christ we already possess, availing ourselves of the help of those who are faithful to that teaching. We have been given Scripture, Tradition, and the Magisterium. God himself has placed guides in our paths to help lead us deeper into the heart of the truth contained therein He does this because the truth is not finally abstract, but a person. What he desires to reveal is not ultimately doctrine, but himself.
The LORD comes,
he comes to rule the earth.
He shall rule the world with justice
and the peoples with his constancy.