A Course in Miracles itself contains some structures. There are for example two basic "levels" or states that are contrasted. There's reality vs illusions, God vs ego, life vs death, awakening vs dreaming, light vs darkness, health vs sickness, heaven vs hell, the Kingdom of God vs Earth.
So let's say that upon reading about these things, we start to form a structure in our mind, sort of a framework. We've got this one box over here in which we put all the reality stuff, and another box next to it but opposite, in which we put all the illusory ego stuff.
Now, here's where a big mistake happens. It's possible to INTERPRET what each of these boxes MAPS to. Or what they refer to in your environment. Whenever the Course says "reality", WHAT in YOUR world view is that REFERRING to? Which PART of your view of all of existence, is it speaking ABOUT? Which means some portion of "existence" in your world view has to be where you put the "reality" box, and another portion has to be where you put the "illusion" box.
If you discern this correctly, you'll map the reality box onto the Kingdom of God which is NOT OF THIS WORLD, and you'll map the illusion box onto THIS WORLD, Earth. This then means that Earth is an illusion. "The world you see is an illusion of a world" "The world was made as an attack on God etc." In this view, "there is no world" is referring to the illusory world which is in turn referring to Earth and all the galaxies etc.
But there is another way to MAP the course. This alternative approach SHIFTS the framework down a level. It considers that all the "reality" box stuff is actually TALKING ABOUT or referring to, THIS WORLD. e.g. the universe, Earth, bodies etc. Everything the course says about real stuff a person will think is referring to THESE THINGS. And here's the rub.
In order for the course ITSELF to seem to make sense, its STRUCTURE has to remain intact - the contrast between the real stuff and the illusory stuff. So that means you now need somewhere to PUT the "box of illusions". SOMETHING in your "environment" has to be ASSIGNED to the box of illusions, otherwise you can't make sense of it at all.
So if Earth and bodies are considered "in the reality box", you now have to find another thing to assign "illusions" to. And what might that be? Well, since if bodies are real we don't want to ever challenge that idea, so it can't be anything PHYSICAL. So this then leans towards something psychological, something perhaps to do with the MIND or the realm of perception. You have to connect the references to illusions SOMEWHERE in your experience.
And so what people do is, they take a necessary "step back" from "the world" which they think is REALITY, Earth, bodies being real, and HAVE TO displace the illusions into some kind of INTERNAL box, a hidden box, a more nebulous perceptual box. And so now the meaning of illusions is RELEGATED entirely to the inside contents of the mind. It all now becomes a model in which illusion means "my FALSE VIEW OF the world", and awakening now must mean "seeing the world as reality".
Of course if the world IS reality, correct perception would SEEM to line up with the idea that all you're supposed to do is learn to LOOK AT the world correctly, "as God intended", and then you're more or less done. ie true perception is now passed off as "seeing the world as God's most beautiful handywork." And therefore that if I don't LIKE the world for some reason, I must be HAVING ILLUSIONS, in my mind, in my perception, which is causing me to NOT APPRECIATE the world that God supposedly created "outside myself."
There is a great deal in the course which COULD by some seem to be suggesting this is correct, especially given that people seem to find themselves ISOLATED to a single body. "The minds are trapped in their brains." And from that perspective, where you think your mind is CONFINED to your brain, or your self is confined to your body, it SEEMS to make sense that the rest of the world and the body are God's creations. It doesn't seem to challenge it. But this is only because the perception of self and mind as LIMITED TO ONE LOCATION goes unchallenged. It's completely ASSUMED that it is normal to find yourself "inside a single body." And in this view, it seems to make sense that "everything else" is God's doing.
But there are some significant distortions that have to be introduced into what ACIM says in order to make this FIT. For example, the course is very clear in stating that "the body does not exist." "The body is a dream". That doesn't fly well if you believe God created the world. So in order to COMPENSATE for that, to ADJUST the course's meaning so that this basic core belief goes unchallenged, a person will REDEFINE THE MEANING of various terms.
"The body" may now be thought of as being some kind of internal "ego attitude" or "mental self". The "world you made" may be considered some kind of projective, perceptual, interpretation OF the world. "Earth" even has to redefined in light of ACIM stating that Earth is heaven's opposite, so now you have to conceive of references to Earth meaning some kind of "inner planet?". Statements about the sun disappearing have to also be reinterpreted to mean some kind of "inner attitude ABOUT the sun". These modifications are absolutely NECESSARY AND UNAVOIDABLE if a person is to try to maintain a sense of CONSISTENCY in their thought system.
But here's the problem. Just because a person is grasping the internal STRUCTURAL relationships in various parts of the course, the relationship between reality and illusions for example, and just because they are maintaining a clear delineation between the two in THEIR view of the world, it doesn't mean their view is VALID. Consistency is not necessarily validity.
It is possible for example, for a person to take *everything* the course says, and essentially RE-MAP it to MAP IT ONTO, this prior-belief that God created THIS world. It takes a huge number of modifications to the meaning of statements to do this, but if a person does this with BELIEF it doesn't matter to them. They just believe it's correct. It SEEMS TO MAKE SENSE to them, because it is CONSISTENT.
But the problem is you can really go DEEP into this and expose yourself over and over and over again to the same interpretation of the course, become very deeply rooted in it, believe you are "getting it", but all the while are interpreting that it is REFERRING TO stuff that it isn't actually referring to. In fact, a person can become extremely comprehensive in their awareness of what the quotes say, studying the text umpteen times, doing the workbook endlessly, and STILL believe that God created the world.
They will think "when it says body, IT MEANS...." and then will attach that to whatever TARGET they think the course is talking ABOUT when it says "body". There is this TRANSLATION happening all the time, which now requires a person to be an expert translator in order to "understand" anything it says. And it's now possible to think you are understanding it because it seems CONSISTENT, while being TOTALLY INVALID. Because if when Jesus says "the body" you think he means "my internal attitude and NOT my physical body", that's now leading to a TOTALLY DIFFERENT interpretation. It now makes the person have to REINTERPRET EVERYTHING, rather than just taking it simply and literally.
What does this DO? It basically establishes in a person's mind a very DETAILED, reinforced, faith-given, heavily-believed-in "model" of what is real and what is not, WHICH IS FALSE. And a person can study the course for DECADES believing that THIS is the correct interpretation of what the course MEANS when it says stuff. What it is REFERRING to. Don't be fooled - someone can have been doing ACIM for 40+ years and be totally mistaken about everything.
So by failing to see what the course is REFERRING TO with each of its statements, an entire layer of interpretation and displacement is occurring which results in the person becoming STUCK AND TRAPPED. They are stuck because they THINK that they are relating to reality, when they are relating to an illusion. They THINK they are accepting what the course is saying, when in fact the stuff they are accepting is REJECTING what the course is saying. And so they think they are doing something they are not doing. WHICH IS INSANITY.
One of the really serious things that happens is this. If it is believed that God created the world, but if this is NOT TRUE, the person believing it now looks upon this world as if it is REALITY. If it is NOT TRUE that this world is reality, but the person believes it is, that person now technically has FALSE PERCEPTION. False perception means you are viewing illusions and mistaking them for reality. Just because a person BELIEVES that this world is reality, doesn't make it true. And believing it is true, is being MISTAKEN, while believing you are NOT mistaken. And so the person becomes BLIND to the fact they are mistaken - they are insane, while believing they are sane.
If the world IS an illusion and you believe it is reality, you are deceived and are believing falsely. But to the person doing this, who believes "the world is real", THEY believe that regarding this world AS REAL is TRUE TO ITS NATURE. That seeing this world "truly" or as God intended, is TRUE perception. So if this world is NOT real, that person now has false perception but believes they have true perception. That is a state of profound confusion.
There are things which the course states plainly enough which are hard to deny. For example it actually states that THE SUN WILL VANISH. It also states that the stars will disappear. Which means, ALL GALAXIES. Believing God MADE THEM this is totally contradictory. What is a person to do? They would have to relegate these references to "they must mean something else". And then they'd seek for something else to pin it on. And good luck with finding "a sun" and a whole bunch of massive galaxies that exists only in your "inner perceptions about the world that's real."
And how about "Both heaven and earth are in your mind"? Surely this isn't saying that your mind is SO VAST that it actually contains a physical planet and an entire kingdom, whereby all of the animals, mountains, oceans, forests are all INSIDE YOUR MIND, meaning your mind must be HUGE and powerful? Well, that's what the Course IS saying. But those who don't believe this, relegate it to a nice comfortable safe "this must just be referring to some perceptions I'm having inside my little body." And that's an extremely TINY (non-threatening) interpretation of what ACIM is meaning.
These are basically the two major views of ACIM. Either God created the world or he did not. If he did, rather large chunks of ACIM **do not mean what they say**. In order to "make it make sense" the whole thing has to be interpreted as poetry, metaphor, and re-interpreted at every turn. Even the meaning of common words HAVE to be completely redefined, like "Earth", "Sun", "Body". Nothing is then taken LITERALLY. The course is no longer believed to be simply plain and obvious or honest and straightforward, but rather some kind of obscure and subtlety poetic array of metaphors that have hidden subtle meanings hardly anyone can understand. And Jesus is quite clear he has taken every effort to make this course as obvious and unambiguous as possible.
The simple view that God did not create this world is FAR MORE ACCURATE, requires massively less "reinterpretation", is EASIER to understand, is much more literally connected to what Jesus actually SAYS using terms that we are familiar with, AND makes a whole lot more sense. The HONEST view of ACIM is that it is telling the truth when it says the sun will vanish, the earth is not heaven, that this world is cruel, and that bodies are illusions. This true view of the course removes an entire LAYER of interpretation and "mapping", taking out the FILTER which some people interpose between themselves and EVERYTHING it says, incapable of taking Jesus at His word EVER.
This view of the course is also far more radical. Therefore potentially more threatening to the ego. It is therefore less popular, and more challenging to accept. If it's true bodies don't exist and the world is fiction and you made it all up and your mind is bigger than the universe ("your mind has the power to make worlds"), that's a much bigger mind bending conclusion with extraordinary implications. It challenges your every belief, all your values, everything you have a special relationship with, the notion of bodies being life forms, and even brings into question whether anything you see is real at all. But this view of the course does have one thing going for it. It doesn't require you to MANGLE THE HELL out of everything it says in order to make it make sense.
"There is no world" is simply literal. "You made sickness and death and can therefore abolish both" is now literal. Miracles can now literally heal the sick and raise the dead IN THE WORLD, not just in your mind. Miracles are no longer mere shifts in perception but capable of transforming matter and BREAKING ALL THE LAWS OF THIS WORLD including the laws of physics, which supports Jesus walking on water LITERALLY. And it also now means that it is possible to overcome PHYSICAL death. And in this view, the world is recognized as AN ILLUSION, NOT the Kingdom of God.
This view of the course is VASTLY DIFFERENT to the conclusions drawn from the other view. The contrast is practically night and day. The THOUGHT SYSTEM that arises is totally different. And the kind of BELIEFS you have to have to invest in them to make them true are TOTALLY opposite. It's literally the difference between believing that God made the Earth and believing God did NOT make the Earth. The difference between THIS IS REALITY, and THIS IS NOT REALITY! It's a hugely different view. And it hugely affects how you perceive and relate to this "world."
You CAN only believe one or the other, if you are consistent about it. Which ever one you side with will completely gravitate ALL your views towards it. In order to keep it consistent, you will HAVE TO adopt every single view that is based on that belief. And that means you will have to view everything "the other camp" believes as TOTALLY FALSE. And not one thing the other camp says will be accepted as true because it would undermine the CORE belief that God made the world, or not. And this is why there is a huge divide in the ACIM community between those who think the world is reality, vs those who do not. It's extremely pivotal and fundamental. And they can't both be true.
So you have taken a side. The question is, whether you are on the side of actual truth, or the side of fiction.