1 John

1 John has no opening greeting, no named sender, and no named recipient, which has led most scholars to treat it as a circulating theological tract or sermon rather than a letter in the ordinary sense, even though tradition groups it with the epistles. Its immediate occasion is a split within the community: "they went out from us, but they did not belong to us," the text says of some who had left, and much of the letter answers a teaching those who left apparently held, that Christ had not truly come "in the flesh," an early denial of Christ's full humanity that later theology would call docetism.

Against this, 1 John insists that whoever denies the Son does not have the Father either, and grounds its authority in eyewitness testimony, "what we have heard, what we have seen with our eyes, what we have looked at and touched with our hands." The letter's most enduring theological claim is its double definition of God as love, "God is love," stated twice, in chapter 4, tying right belief about Christ directly to loving one's fellow believers as an inseparable test of genuine faith: "those who say, I love God, and hate their brothers or sisters, are liars." The letter closes with an unusually direct offer of assurance, writing "so that you may know that you have eternal life," a stated purpose rare in the New Testament's more argumentative epistles.

1 John supplies one of the clearest and best documented cases of a textual addition in the entire New Testament: the Comma Johanneum, a phrase explicitly naming the Father, the Word and the Holy Spirit as three heavenly witnesses, is absent from every Greek manuscript earlier than the late medieval period and from every translation made directly from early Greek texts, appearing first in Latin theological writing and only later inserted into some Latin Vulgate manuscripts and, through them, into the Greek Textus Receptus that underlies the King James Version. Its absence from the early manuscript record is not seriously disputed by textual scholars of any theological position, Catholic, Orthodox or Protestant alike, and modern translations based on critical Greek editions omit it or mark it as a later addition, though it remains printed without comment in Bibles that follow the King James or the Textus Receptus tradition.

Because the verse offered a uniquely explicit trinitarian formula, its removal from modern critical texts has occasionally been treated in popular discussion as an attack on trinitarian doctrine itself, though the doctrine rests on the cumulative witness of many other New Testament passages and does not depend on this one contested verse, a point textual scholars across denominational lines make consistently.