1 John opens up like this:
That which was from the beginning, which we have heard, which we have seen with our eyes, which we have looked at and our hands have touched—this we proclaim concerning the Word of life (1.1).
Critically important here is the apostle's repeated reference to the personal, first-hand experience of him and his associates regarding that which is proclaimed. Dumitru Stăniloae speaks of the preservation and explication of the apostolic tradition through scripture as a apart of testimony to the experience of that same pressure exerted by the integral revelation concentrated in Christ (The Experience of God, vol. 1, p. 64). The apostles felt this pressure, this presence of God's revelation in Christ and afterwards through the Holy Spirit. This is what they confer to us in their testimony through the gospels, the epistles, etc.: the content of that revelation as they received it in Christ. Note John's language here. Their fellowship is with Jesus whom they name Christ and the Son of God (v. 3), and their experiences with him first-hand have left such an impression on them that they go about telling the world about the salutary, life-giving fellowship they have. It's an eternal life (v. 2), a participation in quality of life of the expected eschaton of God's kingdom, and the forgiveness of sins through Christ's death on the cross (v. 7).
This text speaks against two common reasons given by nonbelievers against the testimony of the New Testament regarding Jesus Christ. One group, as exemplified by Fox Mulder from The X-Files, says that the NT is just full of parables and stories which are not intended to be interpreted as literally true. Another group says that the documents were written so long after the purported facts took place that they cannot be trusted to tell us anything about the "real, historical Jesus."
On the contrary, John and his associates heard, saw, and felt Jesus himself; this is what they tell us, this is the claim they make. They saw in him, moreover, the fulfillment of the Jewish eschatological hope in the sovereignty of God over the world; hence they call him the eternal life which was with the Father and has appeared to us (v. 2). Their fellowship is with this Jesus Christ and his Father God (v. 3) -- and since this was written after Jesus' crucifixion and yet they assert that they have fellowship with him, he is putting himself forward as a continuing witness to the fact of Jesus' actual resurrection. Importantly, too, he calls others to have this same fellowship, too, so that they too can come to know this Jesus, the risen Son of God.
Against the "parable" objection, John here plainly takes himself to have come into contact with some actual aspect of reality. He appeals to the senses, claiming that he saw, heard, and felt Jesus, both pre-crucifixion and post-resurrection; and he takes himself to continue to have real fellowship, a salutary life-giving fellowship, with this Jesus and with God the Father. He is not speaking in parables. He is speaking plainly about the real world.
Against the "too long after the fact" objection, again, John here has testified both to a prior witness of Jesus' life, his death, his resurrection, as well as a continued fellowship with Christ. He speaks about the message they received from Christ during his earthly ministry (vv. 5-6), and he speaks about forgiveness through his crucifixion (v. 7). John and his associates take themselves to be in regular fellowship with this Jesus Christ, the one whom they saw alive and dead and then alive again. John puts himself as a witness to all the critical events of Jesus' life.
You may refuse to believe John. You may think horribly deceived about all this. But what you cannot do is try to soften the strength of his claim by making it all parables and myths. More than that, he makes a claim to intimate knowledge of Jesus -- he heard, he saw, he felt -- which you cannot make for yourself. Believe him, or call him a liar, but do not soften what he says so that his claim can just as easily be ignored.