The First Epistle of John, often referred to as First John (US) or One John (UK) (and written 1 John) is a book of the New Testament. This fourth catholic or "general" epistle is attributed to John the Evangelist, traditionally thought to be the author of the Gospel of John and the other two Epistles of John. This Epistle was probably written in Ephesus between the years 95–110. The work was written to counter docetism, which is the belief that Jesus did not come "in the flesh", but only as a spirit. It also defined how Christians are to discern true teachers: by their ethics, their proclamation of Jesus in the flesh, and by their love.

Authorship

The Epistle is traditionally held to have been composed by John the Evangelist, at Ephesus, when the writer was in advanced age. The epistle's content, language and conceptual style are very similar to the Gospel of John, 2 John, and 3 John, indicating that they were written by the same author. Indeed, at the end of the 19th century scholar Ernest DeWitt Burton wrote that there could be "no reasonable doubt" that 1 John and the gospel were written by the same author, and Amos Wilder has said that, "Early Christian tradition and the great majority of modern scholars have agreed on the common authorship of these writings, even where the author has not been identified with the apostle John."