That which was from the beginning, which we have heard, which we have seen with our eyes, which we have looked upon, and our hands have handled, concerning the Word of life…
St. John is not referencing the Scriptures. He is speaking of the living experience of the incarnate Son of God – “which we have heard – which we have seen with our eyes – which we have looked upon – and our hands have handled…” It is this living experience that “we declare to you.” And the purpose of this declaration is more than the relay of information. St. John tells his readers that these things have been declared to them “that you also may have communion with us; and truly our communion is with the Father and with His Son Jesus Christ.” [This is one of those sad verses where English translators have rendered koinonia (κοινωνία) as “fellowship” a meaning that is almost bizarre in its failure to render the Greek.]
The communion to which St. John refers is itself the tradition, the context without which his letter cannot be rightly read. And it is clear that St. John believes that this communion is something that can be given. His word for this transmission is rendered “to declare,” translating the Greek, apaggello (ἀπαγγέλλω – related to the word for gospel). St. John’s declaration is the equivalent of St. Paul’s favorite term, gospel (εὐαγγέλιον, evangel), which is itself frequently misunderstood in its meaning and import.
What does St. Paul mean when he says gospel, the good news? Our first instinct is to find a way to summarize his preaching. Thus the gospel is “Christ died for our sins,” or some such phrase. But St. Paul clearly has an almost global meaning for the word:
For our gospel did not come to you in word only, but also in power, and in the Holy Spirit and in much assurance, (1Th 1:5 NKJ)
It is used to mean God’s revealed plan wrought in the death and resurrection of Christ. It is the preaching of Christ. It is the content of the preaching. But like St. John’s communion, the gospel is not “word only” but also “power.” Thus it is not the proclamation of an idea or a set of ideas, nor the announcement only of an event in history. Gospel is the living power of the communion with the Father through His Son in the Spirit. That living communion is our participation in the crucified and risen Christ.
Source: The Communion of Tradition - Glory to God for All Things