I. Core Theological Concepts (God, Christ, Salvation, and Christian Life):;xNLx;;xNLx;Word of life (1 John 1:1): A title for Jesus Christ, emphasizing Him as the eternal, divine expression of God who is the source of all life, both physical and spiritual. John and the apostles heard, saw, and touched this "Word of life" incarnate.;xNLx;Fellowship (Greek: koinonia) (e.g., 1 John 1:3, 6-7): Sharing in common, communion, partnership, or intimate relationship. John speaks of believers having fellowship with God the Father, with His Son Jesus Christ, and with one another. This fellowship is based on walking in the light and is a mark of true faith.;xNLx;Light (e.g., 1 John 1:5, 7; 2:8-10): A symbol for God's absolute holiness, truth, purity, and righteousness. To "walk in the light" means to live in fellowship with God, in truth and obedience, in contrast to darkness. Jesus is also the true light.;xNLx;Darkness (e.g., 1 John 1:5-6; 2:8-9, 11): A symbol for sin, falsehood, ignorance, evil, and separation from God. Those who claim to have fellowship with God but walk in darkness are lying.;xNLx;Sin (Greek: hamartia) (e.g., 1 John 1:7-10; 2:1-2, 12; 3:4-6, 8-9; 4:10; 5:16-18): Transgression of God's law, lawlessness, moral failure, and anything contrary to God's holy character. John emphasizes that all have sinned, the need for confession, and Christ's work as propitiation for sin. He also states that one who is "born of God" does not make a practice of sinning.;xNLx;Confess (sins / Jesus Christ has come in the flesh) (e.g., 1 John 1:9; 4:2-3, 15; 2 John 7):;xNLx;Confess sins (1:9): To acknowledge, admit, and agree with God about one's sins, which is a condition for receiving forgiveness and cleansing.;xNLx;Confess Jesus (4:2-3, 15): To openly declare and affirm the truth about Jesus Christ, particularly His incarnation (that He came in the flesh), which was a point of contention with false teachers.;xNLx;Cleanse (from sin / from all unrighteousness) (1 John 1:7, 9): To purify from the guilt and defilement of sin, accomplished through the blood of Jesus Christ for those who walk in the light and confess their sins.;xNLx;Propitiation / Expiation (Greek: hilasmos) (1 John 2:2; 4:10): The atoning sacrifice that satisfies God's righteous wrath against sin and makes reconciliation with God possible. Jesus Christ Himself is the propitiation for our sins, and not for ours only but also for the sins of the whole world. His death turns away God's just anger from sinners.;xNLx;Advocate (Greek: parakletos) (1 John 2:1): One who pleads another's cause before a judge, a helper, intercessor, or legal counsel. Jesus Christ is presented as our righteous advocate with the Father when we sin. (The same Greek word is used for the Holy Spirit as "Helper" or "Comforter" in the Gospel of John).;xNLx;Know (God / Christ / the truth) (Greek: ginosko and oida) (e.g., 1 John 2:3-5, 13-14, 18, 20-21, 29; 3:1, 6, 16, 19-20, 24; 4:2, 6-8, 13, 16; 5:2, 13, 15, 18-20): A key theme in 1 John. "Knowing" God or Christ is not merely intellectual assent but an intimate, experiential, and relational knowledge that is demonstrated by obedience to His commandments, loving one another, and abiding in Him.;xNLx;Commandments (of God / of Christ) (e.g., 1 John 2:3-4, 7-8; 3:22-24; 4:21; 5:2-3): God's instructions and moral will, which believers are called to obey as evidence of their love for God and their relationship with Him. Loving God is defined by keeping His commandments.;xNLx;Abide / Remain (in Him / in love / in the light / in death) (Greek: meno) (e.g., 1 John 2:6, 10, 14, 17, 19, 24, 27-28; 3:6, 9, 14-15, 17, 24; 4:12-13, 15-16): To live, dwell, continue, or remain in a close, enduring, and intimate relationship with Christ, with God, in His love, or in His teaching. Abiding in Christ is essential for a fruitful and obedient Christian life and is a mark of true faith.;xNLx;Love (for God / for one another / of the world) (Greek: agape) (e.g., 1 John 2:5, 10, 15; 3:1, 10-11, 13-14, 16-18, 23; Chapter 4:7-21; 5:1-3): A central theme. John emphasizes:;xNLx;God's love for us: Demonstrated supremely in sending His Son as a propitiation for our sins.;xNLx;Our love for God: Shown by keeping His commandments.;xNLx;Our love for fellow believers ("the brothers"): An essential evidence of being born of God and abiding in Him. This love is to be practical and self-sacrificial.;xNLx;Love of the world: Affection for and conformity to the sinful values and desires of the world system, which is incompatible with love for the Father.;xNLx;The world (e.g., 1 John 2:2, 15-17; 3:1, 13, 17; 4:1, 3-5, 9, 14, 17; 5:4-5, 19): In John's writings, "the world" (kosmos) often refers to human society and systems organized in rebellion against God, characterized by sin, darkness, and opposition to Christ and His followers. Believers are not to love the world or the things in the world in this sense.;xNLx;Antichrist / Antichrists (1 John 2:18, 22; 4:3; 2 John 7):;xNLx;Antichrist (singular): A future, ultimate figure of opposition to Christ.;xNLx;Antichrists (plural): Those who deny essential truths about Jesus Christ, particularly His incarnation (that He has come in the flesh), and who oppose His work. John says many such antichrists had already come in his day, often arising from within the Christian community.;xNLx;Anointing (from the Holy One) (Greek: chrisma) (1 John 2:20, 27): A metaphorical term referring to the gift of the Holy Spirit, or the teaching and enlightenment given by the Spirit, to all believers, which enables them to know the truth and discern false teaching.;xNLx;Children of God / Born of God (e.g., 1 John 2:29; 3:1-2, 9-10; 4:4, 6-7; 5:1-4, 18-19): Describes those who have experienced spiritual regeneration through faith in Jesus Christ and have entered into a familial relationship with God as His sons and daughters. This new birth results in a transformed life characterized by righteousness, love for fellow believers, and overcoming the world.;xNLx;Children of the devil (1 John 3:8, 10): Those who persist in sin and oppose God, reflecting the character of the devil.;xNLx;Eternal life (e.g., 1 John 1:2; 2:25; 3:15; 5:11-13, 20): The life of God, a qualitative and unending life that believers receive through faith in Jesus Christ, beginning in the present and continuing into eternity. John writes so that believers may "know that you have eternal life.";xNLx;Truth (e.g., 1 John 1:6, 8; 2:4, 21, 27; 3:18-19; 4:6; 5:6-7, 20; 2 John 1-4; 3 John 1, 3-4, 8, 12): Reality, genuineness, conformity to fact, and especially the revealed truth of God in Jesus Christ and the apostolic teaching. John contrasts truth with lies and deception. Walking in the truth is essential.;xNLx;Lie / Liar (e.g., 1 John 1:6, 10; 2:4, 21-22, 27; 4:20; 5:10): To speak or live falsely, to deny the truth about God, Christ, or oneself (e.g., claiming to be without sin, or denying that Jesus is the Christ).;xNLx;Lawlessness (1 John 3:4): Sin is defined as lawlessness; a rejection or violation of God's law and righteous character.;xNLx;II. Ethical Conduct and Assurance:;xNLx;;xNLx;Obedience / Keep his commandments (See "Commandments" in Section I): A practical outworking of loving God and knowing Him.;xNLx;Righteousness / Practice righteousness (e.g., 1 John 2:1, 29; 3:7, 10, 12): Living in conformity with God's moral will and character. Those born of God practice righteousness.;xNLx;Overcome (the world / the evil one) (e.g., 1 John 2:13-14; 4:4; 5:4-5): To gain victory over the sinful world system and the devil through faith in Jesus Christ.;xNLx;Test / Test the spirits (1 John 4:1): To examine or discern carefully whether teachings or spiritual manifestations originate from God or from a false, deceptive spirit, with the primary test being the confession of Jesus Christ come in the flesh.;xNLx;Confidence / Boldness (before God / in the day of judgment) (e.g., 1 John 2:28; 3:21; 4:17; 5:14): Assurance, courage, and freedom from fear in approaching God in prayer and in facing the future judgment, based on abiding in Christ, a clear conscience, and living in love.;xNLx;Idols (1 John 5:21): Not just physical images, but anything that takes the place of God in one's affections, loyalty, or trust. John ends his letter with a warning to "keep yourselves from idols.";xNLx;This list provides definitions for many of the key terms and concepts encountered in the First Letter of John (ESV). Understanding these within their original context of combating heresy and encouraging genuine Christian living is crucial for grasping John's message of assurance, truth, obedience, and love.