If you look at the various things ACIM says, it becomes clearer and makes more sense when you don't think of "mind" or "one mind" or "christ mind" as being the highest or deepest level of existence. We need to distinguish that mind IS NOT the same thing as spirit, soul, SON or being.
For example, there is a distinction between MIND and SOUL:
"Free will is the attribute of the mind, NOT the Soul. The Soul always remains changeless, because it never leaves the sight of God."
For example, the soul USES the mind to create or miscreate. The mind is at its disposal, like a tool, described here as a MEDIUM *through which* the soul/son/spirit expresses itself:
"The Creation of the Soul is already fully accomplished. The mind, if it votes to do so, becomes a medium by which the Soul can create along the line of its own creation."
For example, we're told that YOU (whatever you are) has control OVER the mind. That mind is the mechanism of decision (free will), and so the "what you are" CONTROLS the mind or has POWER OVER it, meaning it is on another "level", causality-wise:
"For you DO have control over your mind, for the mind is the mechanism of decision. "
All of this indicates that you essentially are OUTSIDE OF your mind. Your mind is something you HAVE, not something you ARE. It's something you USE, and it's not the same thing as your soul.
Soul is a synonym for spirit, and a synonym for "Son of God". So too is BEING an aspect of the soul/son/spirit NOT an aspect of the mind. The essence of what you are at the deepest or highest level, is BEYOND the mind, and CONTAINS the mind inside of it. What you ARE, is the soul/son/spirit/being.
Now look at this:
"Your will is the means by which you determine your own condition, because will is the MECHANISM OF DECISION. It is the power by which you separate or join, and experience pain or joy accordingly. My will cannot overcome yours, because YOURS IS AS POWERFUL AS MINE. If it were not so, the Sons of God would be unequal."
Here, "separation" or "joining" occur WITHIN the realm of your free will, WITHIN the realm of decision, which is WITHIN the mind. Note also that Jesus clearly states your free-will decision is AS POWERFUL AS HIS. That the two of you, EACH, have a free will. Therefore, you both have your own minds.
If you can distinguish these two "levels" within reality, whereby at the highest level there is being/soul/son/spirit, and at the lower level there is MIND, which has IDEAS such as the tiny mad idea, and where ALL ideas are contained INSIDE the mind and do not leave the mind (never affect or determine anything about the soul), then it becomes OBVIOUS that "the ego" is occurring IN THE MIND, NOT IN THE SOUL.
The ego is occurring on an entirely different LEVEL to your soul/spirit/being/son/self.
This means that WHAT you are - a spirit being - is in a larger realm than your MIND, and the ego is never happening in the realm of the spirit. Your SPIRIT does not have a separation idea, the mind does. Your SPIRIT does not develop an ego, the mind THINKS of egotism. Ego is an idea, a thought, in the mind, NOT part of the soul.
Which means... drumroll please... that whether or not there are many SONS, many SOULS, many BEINGS, or many SPIRITS, has absolutely nothing to do with whether or not there is EGO or separation. They're on two entirely different levels. How many sons there are, thus, is completely BEYOND the realm of ego, beyond all speculation as to "it means separation", and beyond all ideas of separateness in the EGO sense. The KIND of separateness that we're trying to undo, has NOTHING WHATSOEVER to do with souls, sons, spirits or beings. We're ONLY trying to correct the MIND, NOT THE SOUL.
The separation is a MIND problem, NOT a soul problem.
And this in turn means, that whether there are many souls/sons, or one, or not, has absolutely nothing to do with the separation or the ego. It is NOT a separation IDEA to suggest that there are many sons, because IDEAS are confined to the MIND, and souls/sons are BEYOND that.
This is why, Jesus is able to tell us in the course that WHAT we are, is permanent brothers, permanent real beings, permanent family, permanent souls, permanent multitudes of spirit beings, and that this fact has NOTHING to do with the ego THOUGHT in the mind.
The ego thought does not come BETWEEN souls, it does not DEFINE their "separateness", it does not CAUSE them to BE separate, and it says absolutely nothing as to the VALIDITY of whether it is NATURAL for there to be many souls in reality. Or therefore, many sons of God. And in fact it also means any statements about "sons of God" plural is absolutely NOT contradictory against ideas of ego separation. They're not even on the same level. Ego is inside the bubble of mind, mind is inside the bubble of being.
"Mind is the activating agent of spirit."
Does not mean mind IS spirit. It's merely a PART of what you are or HAVE.
This is why it's totally OKAY, NATURAL, NORMAL, REAL, and NOT AN EGO THING, that there are MANY SONS OF GOD. And that these son's of God are many in NUMBER *without* it having anything to do with "an ego thing".
God literally has MANY thoughts, in his mind, which is not his being. He literally creates many other BEINGS, and GIVES THEM their own mind, as a reflection of his own nature. Thus God has created many minds, many sons. This is "the family of God".
"Creation is the sum of all God's Thoughts, in number infinite, and everywhere without all limit."
The "One Son of God" is a synonym for Creation, meaning ALL of the sonship. Christ is the MIND that is SHARED in communication between God and the Sonship. SONS are the SOULS/spirits/beings that God created as equals forever (brothers, children of God). And each child has a soul/spirit/being and a MIND with which to create.
Sons of God (meaning God's literal direct descendent IN REALITY) is mentioned 82 times, in direct relationship between God as Father and US (plural) as many BEINGS:
"All the Sons of God"
"We are creation; we the Sons of God."
"Only one equal gift CAN be offered to the equal Sons of God, and that is FULL APPRECIATION."
"Know then the Sons of God, and you will know all Creation."
"When the Atonement has been completed, all talents will be shared by all the Sons of God." (AFTER the ego is GONE, no separation left, there are STILL many sons of God sharing talents!)
"When the Atonement is complete and the whole Sonship is healed…the Holy Spirit will remain with the Sons of God, to bless their creations and keep them in the light of joy." (AFTER the ego, with no separation left, the SONS OF GOD are STILL PLURAL!)
"Our creations are as holy as we are, and we are the Sons of God Himself and therefore as holy as He is."
God creates permanent BEINGS (plural):
"Since only beings of a like order can truly communicate, His Creations naturally communicate WITH Him and communicate LIKE Him."
"God, who encompasses ALL Being, nevertheless created separate beings who have everything individually, but who want to share it to increase their joy. "
God creates permanent CHILDREN (plural):
"God watches over His children and denies them nothing."
"God knows His Children with perfect certainty."
"The Children of Light cannot abide in darkness, for darkness is NOT in them." (no ego!)
"The Children of God are entitled to perfect comfort, which comes from a sense of perfect trust."
"Let us today be children of the truth, and not deny our holy heritage."
"The Kingdom of God includes all His Sons and their children, who are like the Sons as they are like the Father." (not only are there multiple sons, there are multiple CREATIONS BY sons - grandchildren of God).
"Only God's own holy children are worthy to be channels of his beautiful joy"
And similarly there is plenty of mention of SOULS (plural), over 120:
"They represent the original form of communication between God and His Souls"
"It is the final lesson that I learned, and God's Sons are as equal as learners as they are as Souls." (soul=son)
"Souls were given their own true authorship"
"The Revelation unites Souls directly with God."
"In the Creation, God projected his Creative Ability out of Himself toward the Souls which He created, and also imbued them with the same loving wish (or will) to create."
"It should be noted that God has begotten only one Son (the combined totality of ALL the sons). If you believe that all of the ***Souls that God created are His Sons***, and if you also believe that the Sonship is One, then ***every Soul must be a Son of God***, or an integral part of the Sonship." (every means PLURAL! - MANY beings, who SHARE everything).
"They represent the original form of communication between God and His Souls"
"Many Souls offered their efforts on behalf of the Separated Ones" (not all souls used their minds to believe in ego!)
God additionally also created MANY MINDS, not just one:
"God's memory is in our holy minds"
"How holy are our minds!"
"If you allow yourselves to HAVE in your minds only what God put there, you are acknowledging your mind as God created it."
"And peace will be restored forever to the holy minds which God created as His Son" (good example of the ego-rule-breaking logic, that God has many sons who are, IN TOTAL, "His Son").
"Every mind contains all minds, for every mind is one." (still many minds, they don't stop being many just because they are ONE. On means IDENTICAL, of like nature or KIND, NOT one in number).
"all the minds which God created one with me"
"Not being in their Right Minds, they turned their defenses from protection to assault, and acted literally insanely." (MULTIPLE right minds)
The evidence is totally overwhelming for anyone willing to be open to this. It does NOT mean "separation" in the ego sense. It does not mean, ISOLATION, or SPECIALNESS. It only means many EQUAL BEINGS WHO SHARE EVERYTHING AND YET ARE INDIVIDUALS.
There ARE many beings, spirits, souls, sons. There ARE many minds that SHARE as the Christ mind. Ego has NOTHING to do with this. It's NOT unnatural. It's not "wrong". It's not "the separation". Individuality is NOT an ego thing. Ego has ONLY anything to do with whether INDIVIDUALS choose to BELIEVE in lies or truth, WITHIN their minds. That's is all.