Ego's world is run by the egoic thought system, based on an EITHER-OR mindset of separation.
God's world is run by God's thought system, based on a BOTH-AND mindset of sharing.
EITHER-OR is based on the idea of separation - there is a separation between who has and who has not, who does and who does not, what is and what is not, etc. An object is this, but not that. It's either red or blue. It's either here or there.
BOTH-AND is based on sharing, something is equally true of both me and you, we both have everything, me and you are loved the same by God, etc. There is no separation in that. What exists is in all locations simultaneously, space and time do not place limits on anything.
Because the world of physical matter is entirely an expression of the egoic thought system, space and time and everything within them (bodies, planets, etc) are governed by this idea of EITHER OR. Living in such a world, the seemingly "natural" way to think about anything is to align our thought processes to the "natural world" and think in accord with it.
So now we "learn" to think in an EITHER-OR way. Either I will turn left or right. Either I will eat at 5 or at 6. Either I'm male or female. Either I am asleep or awake. Either I choose option A or option B.
We adopt this as an entire way of thinking about the world, of reasoning about anything, of what to do, where to go, what to choose, always a selective judgement based on either this or that. It seems to "fit" well with the way the physical world is structured and how it behaves. But it is completely unnatural and completely opposite to God's world.
In God's world, seemingly miraculous things are possible. Everywhere. All the time. Everything in God's world breaks all the ego's laws of separation, and therefore the entire basis of EITHER-OR thinking. God does not think, hey, either one son or another will get my attention. He thinks, BOTH of them get my FULL attention. Nor does he think, I will give 50% attention to one and 50% to another. He thinks, I will give 100% love to both at the same time. And this is done WITHOUT loss, without sacrifice or lack, and without compromise.
The true meaning of divine sharing is that everything applies to BOTH me and you equally, simultaneously, and always. If there were such a thing as a divine pizza, I could eat the whole pizza and you could eat the whole pizza. We both get everything. This is not possible in the physical world, but it is possible in spirit.
One of the tricky things about understanding ACIM is that we come at it with the ego thought system. We come at it with EITHER-OR thinking. And that's a serious problem. Because whenever ACIM speaks of ANYTHING to do with God, Heaven, Creation, Sonship, Holy Spirit, Laws of God, beyond spacetime, etc.... any of those topics, the laws of GOD are applying, not the laws of ego.
So then a statement like "I and my father are One", is completely misunderstood. It's a truth WITHIN the scope of God's BOTH AND system of thought. There, I can be one with God while still being an individual. I am both, myself and part of God. The course also states that God has only one son, BUT that the one son is also many sons. It literally states that BOTH statements are true, that there is one, and many. The Sonship comprises many children, who are ALSO one.
But to the ego this seems nonsense, it cannot fathom how there can be ONE AND MANY at the same time. It insists that it is EITHER one, OR many. And then it decides that many sounds like an ego thing, and one sounds "more spiritual", so it hacks out the many from the one and ends up with its version of what Heaven must be like. And it's totally bullshit.
To grasp anything of the divine nature of the Kingdom, on ANY topic "that side" of the separation boundary, anything real and true, anything to do with Sonship or Creation or God, you have to totally put aside the EITHER OR exclusive separatist way of reasoning logically, think WAY out side the box, and adopt a BOTH AND way of reasoning. THEN the things that Jesus says that sound totally contradictory finally make perfect sense, WITHOUT having to change anything or turn stuff into ridiculous metaphors.
"One brother is all brothers." "One mind is all minds."
Does not mean there is EITHER one brother OR many brothers. Nor does it mean there is either ONE mind OR many minds. Literally, the entire statement is true. There are many brothers, and they are all one. There many minds, and they are all one. And as soon as your thought process tries to "axe" the "many" part of those statements in favor of keeping only the seemingly unifying "one" part of the statement, you're off on an ego tangent of error.
We are one, but we are still brothers. We are the one son of God, but we are also PART of a sonship of many sons. I am a child of God, and so are you. I have individuality, and so do you, and yet simultaneously we share everything. I have everything that God is, which should to the ego mean there is nothing left for you, but you also have everything that God is, simultaneously, because we share it all. Sharing does not mean a collapse of individuality either.
The BOTH AND system of thought, which "runs heaven", is a completely miraculous thought system. It defies all ego laws. It breaks space and time. It ignores silly limitations and false conclusions. It allows to be possible that which the world of EITHER OR would find absolutely impossible. It ignores spatial limitations of all kinds. This is why God is omnipresent, meaning existing in all locations simultaneously. It ignores the idea that we must be kept apart in order to be individuals. And it defies every attempt to split it up and compartmentalize it into nice little prison cells.
The entire Kingdom of God and everything in it is miraculous because of this fundamental logical premise of the whole system. "Nothing real can be increased (God cannot create) except by sharing". As God SHARES, this is an AND scenario. God AND his creation. God AND his son. BOTH God and His son exist. His son is in his likeness because they BOTH are of the same Kingdom and nature.
When I give to you, BOTH of us have it, and I do not lose it. This is why sharing INCREASES the supply in heaven, while sharing causes scarcity in the ego world. When God creates you, God gives ALL of himself to you and yet loses nothing and HAS everything still - BOTH you and God now share everything and there has been an INCREASE. This is miraculous, it dissolves the idea of separation and exclusivity, transcending all ego concepts. The entirety of reality depends on it.
The system of God's mind, his thought system, how the Kingdom is run, is entirely based on this idea of simultaneous sharing, union at the same time as creation, multiplicity at the same time as oneness, having everything while also sharing it with others without anyone being excluded in any way. Heaven is not like this world. It's laws are totally different to the separated-out world the ego made to depict isolation and selfishness. There is no selfishness in the Kingdom, only self-fullness.
"The ego is the idea of selfishness. The soul is the idea of self-fullness."
You have everything, and we all share it as God's family.