The metaphysics of ACIM is not something that someone made up, it is not an interpretation, it is not subject to someone's opinion, and there is no room for questioning it. It is not one of many possible definitions of the truth. It is THE truth. Either you understand it as it is and accept it as logically true, or you are in denial and confusion.
Metaphysics are FACTS. The thought system of the Holy Spirit is completely logically consistent, as is the thought system of the ego. There is absolutely no room for interpretation. What is "true" can easily be determined by looking at the logical structure of what has happened and where things fit. If you master the metaphysics, you will be able to extrapolate the logical thought system to explain absolutely anything in its correct perspective.
What happens after the separation from God is completely 100% logical. Everything that happens after separation MUST happen, and it MUST happen in a very specific way. The effects of separation are not varied or one possibility among many. There is only one way to separate, there is only one scenario which comes about when separation seems to have happened, and there is only one outcome.
If you can learn the fundamental, completely logically consistent metaphysical structure of the separation, it gives you a framework in which everything else fits into place. A Course in Miracles is teaching this metaphysical structure, but it is not always very obvious. Its obscure nature tends to lead people to not even realize there is a solid "core" to the Course or that you can use this structure to perfectly explain everything the ego does, the meaning of death, and what MUST be true based on it.
For example, separation from God is not possible, because you cannot be somewhere that God is absent. God is everywhere. This immediately tells us that, logically, to believe that this IS possible is insanity. It also must tell us that to believe in such a separation is to believe in a DREAM, a fiction, something which is false or not true and not real. This is already the beginning of some very solid metaphysics, and many people grasp this basic starting point.
But then there is a progression, because as soon as there is a belief in separation, the ENTIRE ego thought system can be logically described and predicted for how it will operate, what it will perceive and believe, what it will value, and everything else about it. Even such things as special relationships, special hate, unconscious guilt and so on, are not just things that happen to be a part of the situation we're in, they MUST ABSOLUTELY FEATURE in an experience of being separate from God. There is a completely LOGICAL progression of thought and circumstance which HAS to come about when there is separation, which leads to all of these things.
Jesus describes some of this in the Laws of Chaos, where he says that first there are separations into individuals/bodies, then this MUST give rise to the perception that each individual is different and therefore lacking, and this MUST then give rise to a sense of competition because others have something you lack, and this MUST mean every individual is sinful for the attack that their "independence" inflicts on each other, and you then end up trying to "get" from others what you lack, by valuing what they lack and trying to possess it - which is the purpose of "specialness" and leads to all special relationships. All of this is a completely logical progression. It's simply what must happen and must unfold based on the separation having taken place.
Another example is what happens right after separation in terms of the split mind and how it becomes at war with itself. If the mind believes in separation, in order to be separate from God, it MUST have separation within itself. There is nowhere else for the separation to be. So the mind becomes divided, believing in "self and other". This MUST mean that WILL is also split, and this MUST mean that both of those parts are in conflict. There are two wills operating seemingly separately or with separate goals, since they logically cannot be the same or in agreement otherwise they could not BE separate. They MUST be at war with each other. They MUST be in a state of conflict. This conflict leads to ALL expressions of war and attack and vengeance and eventual death. It all progresses completely logically.
The metaphysics also shows that what once was a single whole mind, or whole self (Christ), must have become divided and split apart following separation. This mind that believes in separation thus gave rise to multiple illusions of individuals. The illusion of these individuals BEING individual is completely dependent on a strong illusion of the ways they are different, and as this illusion of difference becomes stronger and more established, it turns into what we call "form", which is what the BODY is. So a body is actually a logical progression of the thought system of separation and MUST come about if the separation has happened. Bodies are just very strongly-believed-in fragments of mind appearing separate and unique in order to maintain the ongoing breakdown of wholeness. This is also why bodies are a "picture" of the destruction of Christ, made as separation devices to keep individuals apart and therefore keep Christ from being whole.
There is no guesswork here. There are no opinions. There is no interpretation. This is simply a completely logical, consistent development which takes place. If there is a separation, it has "features" which come from it quite "naturally" and which are completely unavoidable. They are not optional. Bodies, worlds, special relationships, death, sickness, it is ALL a "natural" part of a thought system of separation. The metaphysics recognizes this and gives a perfectly consistent structure to it. The metaphysics can explain WHY all of these things come about.
As you learn the metaphysics, which is somewhat deeper than just "the words" of the Course, you will acquire a kind of template or set of simple laws which you understand to make perfect sense. These can be somewhat abstract so it can require some learning to "generalize" the learning and realize that it's all based on a simple set of logic. But once you then "get" the simple logic, you can now USE that simple logic to examine absolutely any aspect of life, any activity or purpose or way that something happens, and describe it in terms of what the METAPHYSICS says about it, which will be the truth. Irrefutable truth. Provided your grasp of the metaphysics is clear and consistent and you're not making subtle logical errors, the metaphysics gives you VISION to be able to see the truth of what's happening or where things fit together.
For example, recently there have been discussions about whether you can be at peace with death. There were many opinions given. None of the opinions were relevant. The only truth is in what the metaphysics says. In the metaphysical truth, the body is a separation device, it is an illusion, and it is within the mind of Christ. It blocks and hides what is behind it and its only function and purpose is to maintain the illusion of the mind being separate. The metaphysics also tells us that since God is life, and being opposite to God is the separation, separation MUST be death. It also must be a fiction of death - a dream of death. It HAS to be. It also tells us that therefore when the body is "alive", the body is still inside a dream of death. This also tells us that the death which occurs at the end of "life" is just a symbol for death, because what happens before it is also death. This is why Jesus says "death is not an end, it is a continuation."
Also since the metaphysics teaches that death is the opposite of life, and life and peace are one, and therefore death is not peace, we VERY SIMPLY can conclude that it is IMPOSSIBLE for there to be death and peace at the same time. This is irrefutable, perfect logic. This is the truth that the metaphysics tells us. It has nothing to do with anyone's opinion, anyone's lack of understanding, anyone's version of what they think is true based on their so-called experiences, or anything else. It CANNOT be true that death and peace are the same thing or that they truly can be 100% experienced at the same time. Yet many people have tried to justify that they are at peace with death or have come to accept it. They MUST be in denial. The metaphysics makes this clear.
Another simple truth which you can conclude based on the simple metaphysics of separation, is that the split mind is in a state of war BUT it also simultaneously NEEDS that war to continue, in order to maintain a sense of being less than whole and of having an opposite. If truly the opposition were completely wiped out of existence, there would be no more possibility of being at war, and war is entirely founded on being separate and having a split will. So on the one hand, the ego now is constantly trying to attack and be opposed to the "other", but at the same time, it MUST KEEP the other as an enemy for as long as possible. It does not want war to actually SUCCEED, it wants war to be CONTINUOUS.
This is a simple logical conclusion based on the metaphysics of separation. It's not my opinion or someone's interpretation. Therefore all states of conflict and war entail people choosing to suffer for as long as possible. It also means that if one group of people wins the war and totally wipes out the opposition, there would have to be PEACE, because without an opponent there is no basis for fighting. To end the war would thus truly undo the separation, it would be the undoing of those who tried to wage war, and this is not what the ego thought system wants. This is all simple logic. So if someone comes along and has a discussion about war or conflict or attack, if you grasp the metaphysics you can use it to explain what MUST be true about war and conflict.
The separation from God is an entirely CLOSED SYSTEM. There is no room for accidents, there is no room for multiple opinions or interpretations. There is only the FACT of what has happened. You can accept it or you can deny it. If you have a solid grasp of the metaphysics you can DEPEND on it so much that you can TRUST it and you can use it to discern whether people are saying bullshit or whether they are aware of the truth. It also however requires that YOU not be in denial and you not be making logical errors. And the fact is there are a lot of people making a lot of logical errors. Sometimes they are quite subtle. But when someone thinks they know what the truth is but have not quite got it, they will defend it to the death and it must produce war.
Metaphysics reveals that there is only one truth. There is no room for error. There are facts, and that's it. You don't get an opinion. You don't get to interpret it to fit what you want it to be. You don't get to change it. In fact, this extends to your relationship with God and the fact that you keep trying to believe that God has changed His mind about you, or that you can change God. Both must be logically false. But that doesn't stop us believing otherwise, because we are insane. To not get the metaphysics is insanity, and the ego will use it to confuse you and delude you.
There is so much "insight" which can flow out about all kinds of topics if you will just learn the fundamental basic structure of separation. It also reveals to you that there really is only one problem, one dream, one solution. Illusions of how certain things seem different or unique or unlike each other, calling for a special explanation, can be "seen through" if you have the metaphysics right. You will know what to trust, and how to discern. You will be clear about what is true and what is false. You will also be amazed at how you're able to use the metaphysics as a powerful TOOL to give you the truth - what MUST be true - based on what you have learned is logically consistent, EVEN IF you have never thought about the particular topic before. The metaphysics will tell you WHAT IS the truth of the situation, and MUST be true about it, regardless of whether you even believe it yourself.
This logical consistency also builds upon itself. It's like, if you have this blueprint and you use it to place the first few pieces exactly where they belong, then you start being able to draw further logically consistent conclusions from it. It's like a jigsaw puzzle, where if you start out with the correct corners and the correct edge pieces, all of the other pieces can be correctly positioned and discerned, leading to a completely consistent whole picture. It's almost like effortless learning. You don't need to keep learning lots of individual separate modalities or pieces of information. You just get this one 'guidance system' which is the light of truth, the thought system of the Holy Spirit, which puts into perspective absolutely everything else. You switch on this one light and ask IT what is the truth, instead of being in the business of MAKING UP what you want the truth to be all the time, and it will very obviously and clearly tell you exactly what the truth is, from a clear and consistent perspective.
This is also why it is imperative to surrender your egoic attempt to always be the one who decides everything, to always be the one who decides what things mean, to always have your own opinion, to always be running "your own life" which you see as a possession of your own separate from God's will. Trusting Holy Spirit/God is trusting the metaphysics of the truth. The metaphysics completely correlates to the Holy Spirit's thought system. As you trust IT, you are trusting HIM. And as you begin to THINK WITH it, you are thinking WITH HIM, and you will start to have thoughts which are in line with, compatible with, and consistent with, HIS way of thinking, which is perfectly supportive of the metaphysics. The metaphysics of truth IS the way that the mind functions from a true perspective.
So our opinions mean absolutely nothing. Our separate viewpoints are an act of war. Thinking we know that our interpretation of the Course is right, unless it actually IS in line with Holy Spirit's thought system, MUST be a state of denial and MUST entail the authority problem - the ego trying to be the one who determines what is true or not. Only the truth is true. We can accept it, or we can be in denial. If we are in denial, believing we know the truth, we are mistaken. You can accept God's love, or you can reject it, but you cannot change it. You can deny that God is real but that won't change the metaphysics of reality whatsoever. You can pretend all you want, but ultimately, all of reality is a CLOSED SYSTEM with no options and no alternatives. It is what it is. Trying to make it be something it is not, is ego, and WILL produce the illusion of death.