The Epistles of John speak of what is the common life of the believers. Characteristics of the Church, but especially important in these last days?
Here comes more…. when the Lord gives opportunity.
Only this for now:
It is not inconceivable that John, in writing the first letter, had to think back to the time he spent with the Lord Jesus and the disciples. It is very possible that he even specifically thought back to Judas. I expressed that suspicion in the article below about Judas Iscariot.