Around the middle of the 20th century, the tide turned toward translating the Greek word monogenes (μονογενες) in John’s writings as “only,” “unique,” or “one and only.”[i] Prior to that, “only begotten” held sway.[ii] The Baptists freely adopted and used the “only begotten” language.[iii] The use in Confessions does not prove right or wrong, but it does prove the wording was fairly consistently used in many available Baptist Confessions across several centuries.
That Jesus Christ is He which in the beginning did lay the foundation of the heavens and earth which shall perish; that he is Alpha and Omega, the beginning and the end, the first and the last, He is the wisdom of God, which was begotten from everlasting before all creatures... Propositions and Conclusions concerning True Christian Religion, 1614 (John Smyth party that stayed in Holland)
In this Godhead, there is the Father, the Son, and the Spirit; being every one of them one and the same God; and therefore not divided, but distinguished one from another by their several properties; the Father being from Himself, the Son of the Father from everlasting, the Holy Spirit proceeding from the Father and the Son. First London Confession of Faith, 1644/1646
That there is one Lord Jesus Christ, by whom are all things, who is the only begotten Son of God, born of the Virgin Mary; yet as truly David’s Lord, and David’s root, as David’s Son, and David’s Offspring, whom God freely sent into the World (because of his great love unto the World) who as freely gave himself a ransom for all, tasting death for every man, a propitiation for our sins; and not for ours only, but also for the sins of the whole World. The Standard Confession, 1660
The Father is of none, neither Begotten nor Proceeding; the Son is Eternally Begotten of the Father; the Holy Ghost is of the Father, and the Son, proceeding. All Infinite, without Beginning, therefore but one God, who is Indivisible, and not to be divided in Nature, or Being, but distinguished by several Properties and Personal Relations... The Orthodox Creed, 1679
In this divine and infinite Being there are three subsistences, the Father, the Word (or Son) and Holy Spirit, of one substance, power, and Eternity, each having the whole Divine Essence, yet the Essence undivided, the Father is of none neither begotten nor proceeding, the Son is Eternally begotten of the Father, the holy Spirit proceeding from the Father and the Son, all infinite, without beginning, therefore but one God, who is not to be divided in nature and Being; but distinguished by several peculiar, relative properties, and personal relations... Second London Confession of Faith, 1677/1689
We believe, That there is but one only living and true God; that there three Persons in the Godhead, the Father, the Son and the Holy Ghost, Who are equal in nature, power, and glory; and that the Son and the Holy Ghost are as truly and properly God as the Father. These three Divine Persons are distinguished from each other by peculiar relative properties. The distinguishing character and relative property of the First Person is begetting; He has begotten a Son of the same nature with Him, and Who is the express image of His Person; and therefore is with great propriety called the Father. The distinguishing character and relative property of the Second Person is that He is begotten, and He is called the Only Begotten of the Father, and His own proper Son; not a Son by creation as angels and men are, nor by adoption as saints are, nor by office as civil magistrates are, but by nature, by the Father’s eternal generation of Him in the divine nature; and therefore He is truly called the Son. The distinguishing character and relative property of the third person is to be breathed by the Father and the Son, and to proceed from Both, and is very properly called the Spirit or Breath of both. These three distinct Divine Persons, we profess to reverence, serve and worship as the one true God. Declaration of the Faith and Practice of the Church in Carter Lane, 1757
...as the Divine existence is the fountain from which he proceeded, and was the only agency by which his body was begotten, he is called the Son of God; being the only begotten of the Father, and the only incarnation of the Divine Being...the reason why the Divine Father and his only begotten Son are but one Being, is, their nature and attributes, being the same, are infinite and consequently can neither be local nor limited; but what one knows the other knows, and the mind of one is the mind of the other. A Treatise on the Faith of the Free-Will Baptists, 1850
The Mediator, Jesus Christ, the only begotten Son of God, is the divinely appointed mediator between God and man... The Abstract of Principles, 1859
We believe in Jesus Christ, God’s only begotten Son, miraculous in his birth, sinless in his life, making atonement for the sins of the world by his death. We believe in his bodily resurrection, his ascension in to heaven, his perpetual intercession for his people and his personal visible return to the world according to his promise. “Goodchild Confession” of the Fundamental Fellowship of the Northern Baptist Convention, 1921
We believe God so loved the world that He gave His only begotten Son to be the propitiation for the sins of the world, that whosoever believeth in Him should not perish but have eternal life. Eastern District Primitive Baptist Association
We believe that Jesus Christ was begotten of the Holy Ghost in a miraculous manner; born of Mary, a virgin, as no other man was ever born or can ever be born of a woman, and that He is both the Son of God, and God, the Son...We believe that Jesus Christ was begotten of the Holy Ghost in a miraculous manner; born of Mary, a virgin, as no other man was ever born or can ever be born of a woman, and that He is both the Son of God, and God, the Son... Articles of Faith, Baptist Bible Fellowship
We believe in Jesus Christ, God’s only begotten Son, conceived by the Holy Spirit. We believe in His virgin birth, sinless life, miracles and teachings. We believe in His substitutionary atoning death, bodily resurrection, ascension into heaven, perpetual intercession for His people, and personal visible return to earth. Converge (Baptist General Conference)
[ii] From Wycliffe (one begotten) to NASB. The King James verses are: John 1:14 And the Word was made flesh, and dwelt among us, (and we beheld his glory, the glory as of the only begotten of the Father,) full of grace and truth. John 1:18 No man hath seen God at any time; the only begotten Son, which is in the bosom of the Father, he hath declared him. John 3:16 For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life. John 3:18 He that believeth on him is not condemned: but he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God. 1 John 4:9 In this was manifested the love of God toward us, because that God sent his only begotten Son into the world, that we might live through him.
[iii] To me it seems like a lot of people in modern times, unfortunately, are swayed one way or another based on their opinion of the doctrine of eternal generation – rather than the linguistic evidence concerning monogenes. The use of these confessions together does not suggest that they mean the same thing regarding eternal generation.