The fact that Jesus is sometimes called “only begotten” causes a lot of confusion (and is, likewise, emphasized by our Jehovah’s Witness friends).
The King James Version famously says, “For God so loved the world, that he gave his only begotten Son.” John 1:18 in the King James Version also reads, “No man hath seen God at any time; the only begotten Son, which is in the bosom of the Father, he hath declared him.”
If Jesus is the eternal Son of the Trinity, how could he be “begotten”? This is a valid question. I always wondered myself how the early church justified the Son being both eternal and begotten.
First, why are we – today – still saying “begotten”? Can’t we update to “born” already? Have you ever said, “Congratulations on your newly begotten daughter”? But I digress.
Secondly, the Greek word mongenes that is sometimes translated “only begotten” can also be translated as “one and only” (as the NIV does) or “unique” or simply “only” (as the ESV and NRSV do). In fact, if you were to do a study of all the available Bible translations, you’d notice something: It’s usually the older versions that translate it as “only begotten.” Why is this?
This is because Greek scholars used to think the two smaller words that form the compound word monogenes (“mono” + “genes”) meant “only” (mono) and “to beget” (gennao). But after discovering and studying more and more ancient Greek writings, it became clear that the second word wasn’t from the Greek word gennao (to beget), but genos (class, kind). The term monogenes literally means “one of a kind.” To understand monogenes as “only birthed” or “only born” is incorrect. New Testament scholar Michael S. Heiser describes “only begotten” as an “unfortunately confusing translation.”
The definitive Greek to English lexicon (BDAG!) give only two definitions for mongenes: “[pertaining] to being the only one of its kind within a specific relationship, one and only, only” and “[pertaining] to being the only one of its kind or class, unique (in kind).”  Notice, BDAG only gives two definitions for monogenes; neither are “only born.”
BEGOTTEN, NOT MADE
The theologians who created two important creeds of the early church clearly didn’t take “begotten” literally. These creeds were statements of faith based on a close study of the Bible.
In the Nicene Creed (325 AD), Jesus is described as “eternally begotten of the Father.” How can one be eternally born? The creed goes on to describe Jesus as “God from God, Light from Light, true God from true God,” and then they wrote this: “begotten, not made.” Seems to me they’re emphasizing that “begotten” shouldn’t be taken literally.
The main purpose of the Athanasian Creed (500 AD) is to explain the Trinity. It states, “That we worship one God in Trinity… The Father uncreated, the Son uncreated, and the Holy Spirit uncreated…. The Father eternal, the Son eternal, and the Holy Spirit eternal. And yet they are not three eternals, but one Eternal.” It goes on to say, “The Son is of the Father alone, not made, nor created, but begotten.” Clearly, the hardcore Trinitarians that wrote out this long creed to explain the Trinity as precisely as possible didn’t see any contradiction is calling Jesus “eternal” and “uncreated” but also “begotten.” This is a big clue that “begotten” isn’t being used in a literal sense.
Still don’t believe me? God calls Isaac Abraham’s “only son” three times (in Hebrew) during the event of Abraham’s way-too-close sacrifice of Isaac in Genesis 22. Then, the Greek word monogenes is used by the author of Hebrews in the New Testament to describe Abraham’s son Isaac:
“By faith Abraham, when he was tested, offered up Isaac, and he who had received the promises was in the act of offering up his only [monogenes] son.” (Hebrews 11:17)
Isaac was neither Abraham’s only son nor first son. Before Isaac’s birth through Sarah, Abraham had his son Ishmael with Hagar. Monogenes illustrates Isaac’s unique relationship with his father and special status to his father, just as Jesus, God the Son, holds a unique relationship with and special status to God the Father.
*This is an excerpt from my upcoming, vastly revised and expanded edition of Who Jesus Ain’t.
 Arndt, W., Danker, F. W., Bauer, W., & Gingrich, F. W. (2000). A Greek-English lexicon of the New Testament and other early Christian literature (3rd ed., p. 894). Chicago: University of Chicago Press.
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