I am preaching through the Gospel of John in 2021 and in the first chapter we are introduced to two uses of the adjective μονογενής (1:14, 18). Both uses present a challenge to the interpreter:
And the Word became flesh, and dwelt among us, and we saw His glory, glory as of the only begotten from the Father, full of grace and truth (John 1:14 – NASB).
No one has seen God at any time; the only begotten God who is in the bosom of the Father, He has explained Him (John 1:18 – NASB)).
How is God (1:1-2) “begotten?” What is this word and how is it used in the New Testament?
BDAG lists two basic definitions for μονογενής: one and only, only, as well as unique (658). The adjective is used nine times in the New Testament and in two major ways, namely, for referring to a person’s only son or daughter, as well as in referring to God’s only Son. Of the nine uses, four are found with reference to the child of a human (Luke 7:12, 8:42, 9:38; Heb. 11:17). What is interesting is that the remaining five uses of μονογενής to designate God’s only Son are all by John (John 1:14, 18; 3:16, 18; 1 John 4:9).
Older translations had a propensity to translate the adjective according to the two roots that make up the compound (μόνος = “only,” “alone,” and γένος = “descendant,” “family,” “people,” or “class, kind”). As a result, they often rendered it “only begotten” in Johannine uses (NASB, KJV, ASV), arguing that μονογενής was actually made up from μόνος and the verb γεννάω, “to beget.” This has always caused theological concerns since Christ is eternal.
Compound terms are notoriously susceptible to a kind of “root fallacy,” where the supposed original meaning of a word is assigned through history. But words have have no real meaning apart from context, and it is inherently dangerous to appeal to etymology for the lexical force of a word (e.g. “butterfly). Words have meaning in relation to other words. The context of all nine uses of μονογενής help us determine what each author intended.
And what all nine uses of μονογενής do have in common, is that they are used to refer to an only son (or daughter) of someone. In the case of God the Father, Jesus is his one and only, and hence, his unique Son. And the fives uses of μονογενής in John’s uses do emphasis a unique Son at that:
John 1:14: “The μονογενής of the Father”
John 1:18: “The μονογενής God”
John 3:16: “His μονογενής Son”
John 3:18: “The μονογενής Son of God”
1 John 4:9: “His μονογενής Son”
Perhaps D. A. Carson says it best, when, commenting on μονογενής in John 1:14, he writes,
The underlying expression was rendered ‘only-begotten’ Son in earlier translations, but despite the efforts of some to restore that rendering, the NIV is a little closer to what is meant. The glory displayed in the incarnate Word is the kind of glory a father grants to his one and only, best-loved Son—and this ‘father’ is God himself. Thus it is nothing less than God’s glory that John and his friends witnessed in the Word-made-flesh (John, PNTC, 128).
As we look back to the two uses of μονογενής in John 1, we see the uniqueness of the Word made flesh. Jesus, the eternal, all powerful, Creator God became a man (1:14). And in 1:18 we see that this One who was in the bosom of the Father, is none other than the “one and only God” (μονογενὴς θεός).