In Christology, the Logos (Greek: Λόγος, lit. 'word, discourse, or reason') is a name or title of Jesus Christ, seen as the pre-existent second person of the Trinity. The concept derives from John 1:1, which in the Douay–Rheims, King James, New International, and other versions of the Bible, reads:
In the translations, Word is used for Λόγος, although the term is often used transliterated but untranslated in theological discourse.
According to Irenaeus of Lyon (c 130–202) a student of John's disciple Polycarp (c pre-69-156), John the Apostle wrote these words specifically to refute the teachings of Cerinthus, who both resided and taught at Ephesus, the city John settled in following his return from exile on Patmos. Cerinthus believed that the world was created by a power far removed from and ignorant of the Father, and that the Christ descended upon the man Jesus at his baptism, and that strict adherence to the Mosaic Law was absolutely necessary for salvation. Irenaeus writes;
The disciple of the Lord therefore desiring to put an end to all such doctrines, and to establish the rule of truth in the Church, that there is one Almighty God, who made all things by His Word, both visible and invisible; showing at the same time, that by the Word, through whom God made the creation, He also bestowed salvation on the men included in the creation; thus commenced His teaching in the Gospel: "In the beginning was the Word, and the Word was with God, and the Word was God. The same was in the beginning with God. All things were made by Him, and without Him was nothing made. What was made was life in Him, and the life was the light of men. And the light shines in darkness, and the darkness comprehended it not."