There are many key points Matthew Barrett brings up in his 3-part article. The following quotes have help me gain a better understanding of what is meant by eternal generation.
[F]or the Son to be begotten from the Father means that God is begotten from God, which is why the [Nicene] creed confesses the Son to be “true God from true God.”
He is…consubstantial with the Father. Consubstantial means the Son is equal to the Father in every way, from the same essence or substance as the Father, no less divine the Father.
[G]eneration alone is what distinguishes the Son as Son. There is not some other concept or function or activity in the Trinity that distinguishes the person of the Son from the person of the Father. Generation alone can, for it alone conveys the nucleus of sonship.
In his second article in the series, Dr. Barrett tells us what eternal generation it is not. If any of these are incorporated into this theology, it can easily lead to heresy. We see this with cults that claim to be Christian. They veer from the scripture’s teachings about the Trinity and the Person and work of Jesus.
Eternal Generation is not:
Division of nature - because the Father alone is ungenerated, there is no multiplication or division of the divine essence in generation. Division “would sacrifice the full deity of the Son” (Hilary of Poitiers, On the Trinity) Side note: Arians claim that in order for the Son to come from the Father’s essence, the Father must divide Himself or give up some of who He is. They believe Jesus was made out of nothing like the rest of creation. The Jehovah’s Witness teachings about Christ are, at it’s core, from the teachings of Arianism.
Multiplication of essence - if the Father’s essence was multiplied, He could not exist as One and we know that God is One.
Priority and posteriority - To be either would make the Son nonconsubstaintial or not of the “self-same divine essence”. According to Dr. Barrett, if “[t]he Son’s generation …did involve priority or posteriority of any kind, then the Son would be inferior to the Father.” I take this to mean that both priority and posteriority here qualify as a position of rank, coming after as opposed to “from” or “with” the Father, therefore making Jesus less than equal to God.
Mutation
Alteration
Corruption
Diminution
Cessation from operation
The last 5 things on the list involve change as it relates to the nature of God and we know that God does not change. Malachi 3.6
Since the Son is begotten of the Father’s essence, there is 'no partition, or withdrawing, or lessening, or efflux, or extension, or suffering of change, but the birth of living nature from living nature." (Hilary of Poitiers, On the Trinity 6.35 NPNF2 9:111)
In his last article in the series, Undivided Trinity, he quotes Gregory of Nazianzus:
“[Son and Spirit] are from him [Father] though not after him. Being unoriginate necessarily implies being eternal but being eternal does not entail being unoriginated as long as the Father is referred to as origin…so because they [Son and Spirit] have a cause they are not unoriginated. But clearly a cause is not necessarily prior to its effect-the Sun is not prior to its light.” (Gregory of Nazianzus, On God and Christ 3.29.3, p 71)
“In sum, the Father is the principle in the Godhead-the principle who alone is without principle.”
They do not have degrees of being God or degrees of priority over or against one another. They are not sundered in will or divided in power. You cannot find there any of the properties inherent in things divisible. The Godhead exists undivided." ( Gregory of Nazianzus, 4.31.14, p.127)
That is a great question. The only thing I know to say about that is:
We see in John 14.25-26 where Jesus says His Father will send the Holy Spirit
We see in Luke 24.49 where Jesus said He is sending what my Father promised.
And in John 15.26, Jesus says He will send the Advocate Who goes out from the Father.
The Greek word for firstborn is “prototokos” and can mean what it says. In the case of Jesus, however, it means priority to all creation and sovereignty over everything. (aomin.org, Prototokos: It’s Meaning and Usage in the New Testament). When speaking with Jehovah’s Witnesses, you can point out that just because something is firstborn does not automatically imply that it was first created.
I commend you for continuing to witness to these precious people. I know you have been doing this for a while.
I am also interested in what others have to say and if you think anything that has been shared is off target.