When I much was younger, I remember hearing all kinds of conjectures, all rather highly speculative and creative, about why that noun was plural in chapter 4.
The most reasonable explanation to me is this:
Chapter 3 uses “the Lord” to refer to God. Singular. And describes His outlining of his plans to “the intelligences that were organized before the world was”.
At the end of chapter 3, the Lord asks who he should “send”, two volunteer, and the Lord chooses the first one, the one who, on earth, will be known as Jesus.
And then, as the creation starts, the use of plural, begins. Why? Because now there are two involved in the creation of the world: The Father and that first one: the Son.
Why do I think that is the answer to the question about why plural appears here?
Consider the opening verses of the Book of John, which speak of Jesus Christ’s intimate involvement in the creation of the world.
Consider Jesus’ words later, in chapter 5 of the Book of John: “ Verily, truly I tell you, the Son can do nothing by himself; he can do only what he sees his Father doing, because whatever the Father does, the Son also does.”
And consider of the meaning of “Immanuel” by which name Jesus was called by both Isaiah and Matthew; “God with us.”
The God the Father and God the Son were working together in the creation outlined in Abraham chapter 4. Plural.
I think that the reason for that plural is just that simple.
