1 Jn.1:1-7 What was from the beginning, what we have heard, what we have seen with our eyes, what we have looked at and touched with our hands, concerning the Word of Life – (2) and the life was manifested, and we have seen and testify and proclaim to you the eternal life, which was with the Father and was manifested to us – (3) what we have seen and heard we proclaim to you also, so that you too may have fellowship with us; and indeed, our fellowship is with the Father, and with His Son Jesus Christ. (4) These things we write, so that our joy may be made complete.
It is important to understand that John was writing this letter to correct error that had worked its way into the early church by way of Gnostic influence that had become prevalent in the first century. In their view, the physical appearance of Jesus was replaced with a some form of supernatural, spiritual vision. Along with this, they either stressed that all physical reality and pleasure was bad (was to be denied) and only the spiritual realm was of value or they emphasized that one is free to do anything they want to do in the physical realm as long as they also gave attention to their spiritual wellbeing (the two were utterly unrelated). Many of the statements made by John in this letter find clarification when understood as an effort to correct these errors.
Though we do not currently struggles with Gnostics in an official manner, we can see that ideas about the relationship between our spiritual life and physical existence / activity continue to present a struggle within our culture and the Christian community.
John indicates that embracing such error will ruin fellowship within the Christian community, with the Father and with the Son as he states that he writes to correct such error “so that you too may have fellowship with us” and, thereby, “our joy may be complete” (vss.3b and 4)
(5) This is the message we have heard from Him and announce to you, that God is Light, and in Him there is no darkness at all. (6) If we say that we have fellowship with Him and yet walk in the darkness, we lie and do not practice the truth; (7) but if we walk in the Light as He Himself is in the Light, we have fellowship with one another, and the blood of Jesus His Son cleanses us from all sin.
It would seem that John indicates that the teaching he picked up from Jesus emphasized the moral purity of God (“God is Light). “Light” has reference to moral truth and purity while darkness would refer to a denial of or refusal to live according to moral truth. Once again, as a branch of the Gnostic community taught that behavior had no impact on one’s spirituality, John countered this by indicating that one cannot have fellowship with God (spiritual reality) if one walked in darkness. The word “walk” implies a path, beaten or trampled track. This is not just a one-time walk down an aisle but a persistent course or pattern in one’s life. In the process of encouraging fellowship with “one another” and with the Father and the Son, he contrasts walking in darkness with practicing or doing (present, active, indicative) – the truth.
We close this post by considering that John states that “the blood of Jesus His Son cleanses us from all sin” as we pursue fellowship with God in the light.
 “The word ποιουμεν is the 1st person plural form of the verb marked similar below. Its tense is present (which indicates that the action is in the now), its voice is active (which indicates that the subject performs the action, instead of receives it), and its mood is indicative (which describes a situation that actually is — as opposed to a situation that might be, is wished for, or is commanded to be).” – Abarim Publications; Interlinear Greek/English New Testament