What Does John Mean by Knowing God in 1 John, Part 4
Let’s continue with our study in 1 John. We left off last time introducing the purpose for the apostle John writing 1 John. As he did in the gospel of John, he emphasizes the deity of Jesus. He spends much of his time in 1 John pointing out the fact that Christians not only have the privilege of being in fellowship with Christ by virtue of the fact that we have salvation, but he encourages us to pursue fellowship with God because it is not automatic. It is something that Christians must work toward. This theme is constant throughout much of the letters of the New Testament, whether from Paul, Peter, John or someone else. Fellowship is the area for the Christian that is most important once salvation is received. Yet, all too often, it is an untried and untested commodity due to the Christian’s failure to enter into fellowship for a variety of reasons, which we discussed last time.
In 1 John, the apostle begins his letter almost the same way he began his gospel account. He focuses on the incarnate Word, Jesus.
This is what we proclaim to you: what was from the beginning, what we have heard, what we have seen with our eyes, what we have looked at and our hands have touched (concerning the word of life— 2 and the life was revealed, and we have seen and testify and announce to you the eternal life that was with the Father and was revealed to us). 3 What we have seen and heard we announce to you too, so that you may have fellowship with us (and indeed our fellowship is with the Father and with his Son Jesus Christ). 4 Thus we are writing these things so that our joy may be complete – 1 John 1:1-4.
John makes several cogent points in his introductory remarks. He states that Jesus had a physical body (“our hands have touched”), and that he was a human being in every way. John says that “we” (he, the other apostles, and other believers who were physically witness to Jesus’ life) heard Jesus speak, saw Him with their eyes, and touched Him. These facts are an immediate renunciation of the Docetism’s heresy (a form of Gnosticism), that Jesus was a phantom, ghost, or theophany who simply walked among people for a brief times appearing to be a human being, but was merely a ghost. To this, John asserts that Jesus was real. There can be no denying it.
Moreover, Jesus is Eternal Life (v. 2). The life that was Jesus Christ – who came in the flesh – is eternal life and Jesus existed with the Father before He came to this earth in the form of a human being. To John, the fact that Jesus existed before He took on human form and that He existed with the Father is proof that Jesus is God. He presents this information as facts that are not up for debate. John was an eye-witness to Jesus and His ministry. This is not an account by someone who heard about Jesus (though those accounts can be and are useful for us as well). John’s account is firsthand knowledge and experience.
But John is also quick to point out that all of the information he presents about Jesus in verses 1 through 3 he writes in order for his readers to understand that it is God’s desire to have fellowship with one another as we have fellowship with God, both the Father and with Jesus Christ, the Son. This is extremely important for us to realize, understand, and know. We are to have fellowship with one another just as we have fellowship with God. This is the purpose of John’s epistle. He wants to impart specific knowledge regarding our fellowship so that “our joy may be complete.” Whose joy? John’s as well as the joy of the believers to whom he is writing. The use of the “our” here is simply to include himself as part of that particular congregation.
Joy in fellowship cannot exist unless several things happen. First, error about Jesus must be excluded. This is why John tackles the Docetic error right off the bat by putting forth the fact that Jesus was alive and well and walked among people as a Person Himself. He was not a ghost, a phantom, or a theophany. He was a real human being who suffered in His humanity to perfect us via the atonement. Moreover, if we stop to consider it, Jesus was tempted in all ways as we are during His earthly life (Hebrews 4:15), yet remained sinless. He was fully human and experienced hunger, fatigue, and many other aspects of being human. Yet, in spite of all these things, He remained sinless and was, at the end, able to offer Himself as a perfect sacrifice for our sins, and did so.
We cannot hope to have fellowship with other people who simply believe in some ethereal form of a god, but do not believe that Jesus – God the Son – came in the flesh as the God-Man to live a sinless life and die a criminal’s death on the cross. That kind of fellowship is impossible because the beliefs are so diametrically opposed to the truth presented in Scripture. While there are certainly some things in Scripture that provide us wiggle room as far as beliefs are concerned, but on the deity of Christ, there is no such wiggle room. Either people see and accept Jesus as God the Son, though fully human, or they do not. We cannot hope to have fellowship with people who reject the deity of Jesus. Because John comes out so forcefully at the beginning of his letter, we can assume the great importance of this truth.
It is also very interesting that in these opening verses, he unites God the Father with God the Son. By doing so, he repudiates the belief that people can have any sort of fellowship with God apart from Jesus. The two go hand-in-hand. You cannot have one without the other because both are represented in the Godhead.
John wrote this epistle so his readers might join and continue in the fellowship with God that is possible only for those who have seen God, as the apostolic eyewitnesses of the incarnate Christ had done. 
It is, unfortunately, clear that the purpose for John writing to this flock was to combat the error put forth by false teachers whose teachings were not in line with the truth. It is impossible for Christians to fellowship with other Christians who do not hold to the truth about Jesus. In fact, the belief that Jesus is not God is Antichrist, as John will get to later in 1 John 4:3. In order to fellowship with other believers, there must be this common belief, that Jesus is God and that He came in the flesh.
This is really the entire reason John wrote this epistle, which was to unite people of faith under the same truth. He did so by standing against the error that claimed Jesus was not God and/or did not come in the flesh as a Man. As an apostolic eye-witness to the life, ministry, and death of Jesus, John – like the other apostles – was in the unique position to call out error and move people away from it, which is what he endeavored to do here in this epistle.
John’s point is that we must remove ourselves from the error that says either Jesus did not come in the flesh, that He was not God, or both, in order to begin enjoying fellowship, both with God and with other Christians. Those who do not believe Jesus is the God-Man can certainly not have fellowship with Him because they are in unbelief regarding His nature. This truth is foundational and paramount to entering into fellowship with God in Christ. It is absolutely imperative that we understand exactly who Jesus was (and remains). Without this proper understanding, we will not have fellowship with God at all and certainly our fellowship with other believers will also not be what it could be.
Pastors and teachers need to firmly and lovingly correct this particular error whenever it tries to rear its satanically-inspired head. It is a lie from the pit of hell and must not be tolerated.
We’ll return to continue moving through 1 John.
 Dr. Thomas L. Constable’s Notes on 1 John (2015 edition), p. 11