The following lengthy excerpt is taken from Wayne Grudem’s Systematic Theoolgy (Second Edition): An Introduction to Biblical Doctrine, published by Zondervan Academic, Grand Rapids, MI 2020, Part 2: The Doctrine of God, Chapter 14. God in Three Persons: The Trinity, pp. 293-298.
“In John 3:16, Jesus is said to be God’s ‘only-begotten Son’ in three translations: ‘For God so loved the world, that He gave His only begotten Son, that whoever believes in Him should not perish, but have eternal life’ (John 3:16 NASB; KJV and NKJV also have ‘only begotten.’).
“But most modern translations do not say ‘only begotten Son.’ All of the other widely used English translations simply say ‘only Son’ or ‘one and only Son,’ with no notion of begetting: ‘For God so loved the world, that he gave his only Son, that whoever believes in him should not perish but have eternal life’ (John 3:16 ESV; similarly, RSV and NRSV, while CSB, NET, NIV, and NLT all have ‘one and only Son’). The difference in translation is due to different understandings of the underlying Greek word which occurs here and in four other verses. Historically, the word was understood to mean ‘only begotten,’ with mono meaning ‘only’ and genes as an adjective related to the verb gennao, ‘to beget, to bear,’ a verb commonly used to refer to the father’s (or less commonly the mother’s) role in the birth of a child.
“However, beginning in 1886, various New Testament scholars challenged the meaning ‘only begotten,’ arguing that the word carries no suggestion of ‘begetting’ and that it should be understood to mean ‘only, unique, one of a kind.’ They argued that the second half of the word is not closely related to the verb gennao (‘beget,’ ‘bear’; spelled with two n’s) but rather to the term genos (‘class,’ ‘kind’; spelled with one n). Thus the verse refers not to the ‘only begotten’ Son but to the ‘one-of-a-kind’ or ‘unique’ Son. These arguments have seemed persuasive to most Bible translation committees. I too adopted the translation ‘only’ because it was favored by the Bauer-Danker-Arndt-Gingrich Greek-English Lexicon, several translations, and a large majority of commentaries. I also added an appendix defending the translation ‘only’ to the first edition of this book. I recommended that it would be better not to speak of the ‘eternal begetting (or generation) of the Son.’
“But then, in 2017, substantial new evidence came to light. Charles Lee Irons published a significant essay, ‘A Lexical Defense of the Johannine “Only Begotten.”’ Irons reported that he had found many hundreds of examples of monogenes in the early church fathers who wrote in Greek. He then pointed to B. F. Westcott’s 1886 commentary on the epistles of John as the earliest support for the meaning ‘unique’ rather than ‘only begotten.’ Westcott was followed by other publications, and eventually the meaning ‘only’ appeared in these five verses in the RSV in 1946, and other Bible translations followed.
“In response to the ‘only, unique’ view, Irons argues that the difference between single and double n in genos and gennao has no significance since both words ultimately share the same root and the doubling of n is a common spelling variation in Greek.
“Significantly, Irons found ‘at least 145’ words in ancient Greek that are built upon the –genes stem. By far the largest number of them have the idea of being born or produced. These include thalassogenes (“sea-born”), neogenes (“newborn”), patrogenes (“begotten of the father”), proteregenes (“born sooner, older”), and purigenes (“born in or from fire”). He says, ‘Fewer than 12 of the 145 –genes words involve meanings related to “kind”.’
“Irons does not claim that monogenes always means ‘only begotten,’ because there are numerous clear examples where it does mean simply ‘only, unique, one-of-a-kind.’ But Irons is claiming that many hundreds of examples prove that it certainly can mean ‘only begotten,’ and that ‘monogenes is used more basically and frequently in reference to an only child begotten by a parent, with the implication of not having siblings.’
“He adds another argument:
If the word meant ‘only,’ then we would expect to find it used to modify many other nouns that do not involve the concept of begotten or being an offspring, for example, ‘only wife,’ ‘only brother,’ only friend,’ ‘only slave’…‘only garment,’ ‘only house,’ ‘only sword,’ and so on. But such collocations are completely absent in extrabiblical Greek. This suggests that the literal meaning…is the straightforward biological meaning: ‘only begotten,’ that is, ‘without siblings.’
“Irons then explains that ‘this basic meaning gets gradually extended in ever new non-literal, metaphorical directions,’ including the meaning ‘only legitimate child or heir’ (applied to Isaac in Heb. 11:17) and eventually the meaning ‘only one of its kind.’
“Finally, Irons considers the meaning of monogenes in the New Testament. John 1:14 is especially significant: ‘The Word became flesh and dwelt among us, and we have seen his glory, glory as of the only Son from the Father, full of grace and truth’ (John 1:14). The problem is that the word son (Gk. huios) is not in the Greek text, which just says doxan hos monogenes para patros. If we translate monogenes as ‘only,’ we end up with the nonsense phrase, ‘glory as of the only from the Father.’ When Bible translations such as the ESV and NIV have to insert the word ‘Son,’ Irons says, they show that monogenes cannot mean simply ‘only’ in this case but that the notion of being a child or being begotten was part of the meaning signified by the word monogenes itself. By contrast, the translation ‘glory of the only begotten of the Father’ is a coherent idea.
“In addition, the view that Christ was eternally begotten by the Father is explicitly affirmed in the Nicene Creed, which has been widely used by Christians since it was first written in AD 325 (and revised in AD 381). It begins this way:
I believe in one God the Father Almighty; Maker of heaven and earth, and of all things visible and invisible.
And in one Lord Jesus Christ, the only begotten [Gr. monogenes] Son of God, begotten of the Father before all ages, God of God, Light of light, very God of very God, begotten, not made, being of one substance with the Father; by whom all things were made.
“Clearly, the authors of the Nicene Creed understood monogenes to mean ‘only begotten,’ not just ‘only, unique,’ because they use the verb gennao (‘beget’) twice to explain what monogenes means: (1) it is an eternal begetting that never had a beginning because Christ was ‘begotten (gennethenta) of the Father before all ages,’ and (2) it does not mean that the Son was created, for the Son was ‘begotten, not made (gennethenta, ou poiethenta).
“The evidence and arguments produced by Irons have convinced me that monogenes when used of God the Son in the New Testament means ‘only begotten.’ As a result, I have removed appendix 6 (where I argued against ‘only begotten’) from this edition of Systematic Theology. In addition, I am now willing to affirm the doctrine of the eternal generation of the Son (also called the eternal begetting of the Son).
- The Meaning of the Eternal Generation of the Son
“As indicated in the previous section, I now think the following verses (and John 3:18; 1 John 4:9) should be translated to reflect the meaning ‘only begotten’ for the Greek word monogenes:
And the Word became flesh and dwelt among us, and we have seen his glory, the glory as of the only begotten from the Father, full of grace and truth. (John 1:14)
No one has ever seen God; the only begotten God, who is at the Father’s side, he has made him known. (John 1:18)
For God so loved the world, that he gave his only begotten Son, that whoever believes in him should not perish but have eternal life. (John 3:16)
“But what can it mean that Christ is God’s ‘only begotten Son’? Because so many other passages affirm the full deity of Christ (see section B.2 above, and chapter 26), and because God has existed eternally, we must stay away from any idea that the Son was somehow created by the Father in the distant past. In this respect the analogy with human begetting breaks down and does not apply.
“On the other hand, the examples in the previous section show that the compound words using –genes tend to carry an implication of some kind of origin. And there are other verses that speak of the Son as existing in some sense ‘from’ the Father: Christ is ‘the radiance of the glory of God and the exact imprint of his nature (Heb. 1:3). The word radiance (Gr. apaugasma) gives the sense of bright light shining from a source of light, and exact imprint (Gr. charakter) is a word elsewhere used for an exact duplicate of an original pattern (such as a coin stamped out at a mint). Both words indicate that the Son, while not created, is in some sense ‘from’ the Father. Similarly, the Son is said to be the ‘Word’ of God (John 1:1-2), and a word is something that is spoken outward from a person. And John quotes Jesus as saying, ‘For as the Father has life in himself, so he has granted the Son to have life in himself’ (John 5:26).
“Bruce Ware, I think rightly, adds the following argument for eternal generation: ‘Since the Father is really Father, as opposed to being Father nominally (i.e., in name only), and since the Father is eternal Father, then it follows that he must really have a Son, who is genuinely from Him (otherwise He isn’t really Father), and that this Son from Him must likewise be eternally from Him (otherwise He isn’t eternally Father).’
“What, then, does the eternal generation of the Son mean? It means that the Son is in some sense ‘from’ the Father. But beyond that, it is easier to define what it does not mean than to clearly explain what it does mean. Eternal generation is not something that ever began, but it is eternal. It does not mean that the Son was created by the Father. And it does not mean that the Father possesses any of the attributes of God in a greater measure than the Son.
“Speaking positively, we can say that the eternal generation of the Son implies that (1) the Son is of the same essence as the Father (for a father begets a son like himself), (2) the Son is a distinct person from the Father (for the Son is begotten and the Father is unbegotten), and (3) there is a specific order in the relationship between Father and Son (the biblical pattern is always from the Father through the Son, as in 1 Cor. 8:6). But all three of these points can be established from the clear testimony of many passages of Scripture without any need for a doctrine of eternal generation (as is evident, for example, from the fact that I affirmed all three of these points in the first edition of this book while denying eternal generation). Still, the idea of the eternal generation of the Son implies all three of these points at once, while otherwise they would have to be established by a combination of the teachings of several different verses.
“Can we explain anything more about what happens in this eternal generation? What kind of generation is this? There have been at least two common explanations that do not clearly contradict any text of Scripture or any essential element in the doctrine of the Trinity:
- Eternal generation means that the Father eternally communicates to the Son the divine essence, so that the Son fully shares in every attribute of the Father. John 5:26 can be understood to support this idea: ‘For as the Father has life in himself, so he has granted the Son also to have life in himself.’ This does not mean that the Father is greater than the Son in any attribute, for the Father’s communication of the divine essence is so complete that the Son is the ‘exact imprint’ (or exact duplicate) of the Father (Heb. 1:3). And because this generation is eternal, the Son was not created but eternally existed as ‘the only begotten Son.’ This has been the most common view through the history of the church.
- Eternal generation means that the Father is the source of the personal distinctions between Father and Son (and, by implication, the Holy Spirit), but he is not the source of their divine essence (or being). This was the view of John Calvin, who was concerned that the first option (saying that the Father communicates the divine essence to the Son) seems to imply that the Son and Spirit are lesser deities, that they somehow do not fully have all the attributes of the Father.
“I find it difficult to decide between these two options, but option (a) seems to be a more natural conclusion from the meaning ‘only begotten’ (John 1:14, 18; 3:16), from the very names Father and Son, and from verses that speak of the Son as the Word of God (John 1:1-2), ‘the radiance of the glory of God and the exact imprint of his nature’ (Heb. 1:3), and the one whom the Father has granted to ‘have life in himself’ (John 5:26).
“However, I am not convinced that God has revealed enough information in Scripture for us to affirm or deny either option (a) or (b) with confidence. The actual meaning of the eternal generation of the Son might in fact be option (c), an explanation that we do not now understand or even know about. What we do have is five verses that say that Christ is the ‘only begotten’ Son of the Father, and we have other verses that teach that God is eternal. Therefore, we can affirm with confidence the eternal generation of the Son. But we are dealing here with a topic of great mystery, and it seems wise to admit that much of this topic remains among the ‘secret things’ that ‘belong to the Lord our God’ (Deut. 29:29).”