WRITER, The Apostle John. 
PLACE AND DATE UNCERTAIN. Probably written from Ephesus near the end of the first century.
TO WHOM ADDRESSED. Apparently to the church at large, as it has no greetings, farewells or other personal allusions; hence it belongs to the "general epistles."
It calls believers by affectionate titles, as "LITTLE CHILDREN,"
1Jo 2:1,18,28 3:7,18 4:4 5:21
and "BELOVED."
1Jo 3:2,21 4:1,7,11
PURPOSES. The writer mentions four reasons for writing this epistle to Believers.
Viz: To add to their joy
1Jo 1:4
to guard them against sin
1Jo 2:1
to warn them against false teachers
1Jo 2:26
to strengthen their faith in Christ and assure them of eternal life
1Jo 5:13
KEY WORDS, "Fellowship," "Know," "Love."
CENTRAL THEME, God is Life, Light, and Righteous Love. His character calls for holy living and brotherly love on the part of
believers.
DISTINCTIVE CHARACTERISTICS.
This may be entitled, "The Epistle of Certainties."
It opens with a positive statement of experimental knowledge of Christ
1Jo 1:1-3
It lays great stress upon the spiritual knowledge obtainable by believers. The word "Know," or its equivalent, appears over thirty times.
We have selected seven important instances where the words "We know," appear.
"We Know"
(1) That a righteous life indicates regeneration
1Jo 2:29 5:18
(2) That we shall be like Christ at his coming
1Jo 3:2
(3) That Christ came to take away our sins
1Jo 3:5
(4) That brotherly love indicates that we have passed from death unto life
1Jo 3:14
(5) That he abideth in us by the witness of the Spirit
1Jo 3:24
(6) That we have eternal life
1Jo 5:13
(7) That our prayers are answered
1Jo 5:15
SYNOPSIS.
PART I. God is Life and Light.
Ch. 1.
(1) Manifested in Christ
1Jo 1:1,2
(2) The purpose of the epistle
1Jo 1:3,4
(3) Conditions of divine fellowship.
(a) Walking in the light
1Jo 1:5-7
(b) Confession of sin
1Jo 1:8-10
Ch. 2.
(c) Acceptance of Christ as advocate and propitiatory sacrifice
1Jo 2:1,2
(4) Obedience the test of fellowship.
(a) Following Christ's example
1Jo 2:3-6
(b) Obedience to the new commandment of love, is abiding in the light
1Jo 2:7-11
(5) A message to different classes of believers concerning spiritual knowledge and overcoming the wicked one
1Jo 2:12-14
(6) A warning against the love of the world
1Jo 2:15-17
(7) The rise of antichrists, their apostasy, and denial of Christ, is a sign of the last time
1Jo 2:18-23
(8) An exhortation to abide in the truth, with the assurance that the divine anointing will give all needed instruction
1Jo 2:24-27
(9) Abiding gives confidence, and righteousness is a mark of the new birth
1Jo 2:28,29
PART II. God is Righteous Love.
Ch. 3.
(1) His love manifested in the exaltation of believers to sonship
1Jo 3:1,2
(2) The test of sonship is righteous living
1Jo 3:10
(3) Brotherly love the distinguishing mark of spiritual life
1Jo 3:11-15
(4) Love manifests itself in sacrifice, not in words only
1Jo 3:16-18
(5) The outcome of love is assurance and answered prayer
1Jo 3:19-22
(6) Faith and brotherly love essential to fellowship with God
1Jo 3:23,24
Ch. 4.
(7) Parenthesis. The spirits of truth and error in the world and the methods of testing them
(a) Their attitude toward the incarnation of Christ determines their origin and character
1Jo 4:1-3
(b) The world-marks of antichrists
1Jo 3:4-6
(8) The divine love.
(a) In the human heart indicates regeneration
1Jo 4:7
(b) Manifested in the incarnation and sacrificial work of Christ
1Jo 4:8-10
(c) Indwelling in believers begets brotherly love, and inspires testimony concerning Christ as Saviour of mankind
1Jo 4:11-16
(d) When perfected gives assurance and casts out fear
1Jo 4:17,18
(e) Kindles love to God and brotherly love
1Jo 4:19-21
PART III. Faith and Love the Overcoming Principles in the Conflict
with the World and All Evil Powers.
Ch. 5.
(1) The love-life of obedience
1Jo 5:1-3
(2) The victory of faith
1Jo 5:4,5
(3) The divine witnesses in earth and heaven
1Jo 5:6-9
(4) The witness of the Spirit
1Jo 5:10
(5) The gift of eternal life through the Son of God
1Jo 5:11-13
(6) The certainty of answered prayer
1Jo 5:14,15
(7) Dealing with the sinful brother
1Jo 5:16
(8) The believer's four-fold knowledge
1Jo 5:18-20
(Outline from Thompson’s Chain Reference Bible)