1 John 1:1-4 reads, “That which was from the beginning, which we have heard, which we have seen with our eyes, which we looked upon and have touched with our hands, concerning the word of life— the life was made manifest, and we have seen it, and testify to it and proclaim to you the eternal life, which was with the Father and was made manifest to us— that which we have seen and heard we proclaim also to you, so that you too may have fellowship with us; and indeed our fellowship is with the Father and with His Son Jesus Christ. And we are writing these things so that our joy may be complete” (ESV).
Once again, we have a distinction between those who were with Jesus as eyewitnesses — saw with their own eyes, heard, and touched concerning the Word of life. They got it first hand. But, John explains that he and the others proclaim what they saw and heard to others in Christ so they can have fellowship with them. How can they have fellowship? Does the Lord visit them with revelations? Does He send His message in a dream or vision? Does He reveal truth through any other means than the human agency of inspired apostles? If they did not have fellowship in any other way than by the teaching of the apostles, why would we expect God to speak directly to us? If John believed that Jesus could speak to them directly or through dreams (instead of through the testimony and revelation of His eyewitnesses), the distinction made by John would be meaningless. Who cares if John reminds them or not? If they have revelation from God and Jesus speaks to them, they do not need John or any other apostle. But, clearly, their fellowship rested in the work of these men and the revelation they left behind. Without them, there is no fellowship.