The world was made as an attack on God. It symbolizes fear. And what is fear except love's absence? Thus the world was meant to be a place where God could enter not, and where His Son could be apart from Him."
...This section of the Course is interesting. It clearly says that "the world IS false perception", having not left the mind. In other words, the world is inside the mind, is made of mind-stuff/images/illusions, and is not physically real or objectively real. But notice it says the world *IS* false perception, not just that you are misperceiving a world.
Notice also it doesn't say the world is 'out there' and you PERCEIVE IT falsely. The world ITSELF IS perception. Your perceiving hallucinates a world, because "projection makes perception". Projection making perception does NOT mean that you are just projecting ONTO the world and perceiving things that are not there, it means that you are projecting THE WORLD ITSELF and are then perceiving it. Your interpretations of what you then PERCEIVE is just another LAYER of projection on top of the projected world. You are projecting the world in your mind and THEN you perceive it with the body.
This is an important distinction because so many Course folks are thinking that you just need to fix your perception OF something that exists kind of on its own, and that if you can get the right perception of it then you'll be in reality. That's not how it works. The world seeming to exist AT ALL is because of perception, which is false.
When the thought of separation (which hallucinated the world) is seen in another light (ie right-minded perception), you may see the forgiven world (which is lovely), BUT only as a stepping stone to LEAD TO the truth, "where all the world must disappear".
"WHERE ALL THE WORLD MUST DISAPPEAR". Because it's not real to begin with. It's just a great big IDEA of separation in the mind.
"Now its source has gone, and its effects are gone as well". Its source is the idea of separation, and the effect of that idea was the hallucination of a world existing. Not just a hallucination ABOUT a pre-existing world or on TOP of a world, but THE world itself.
I think one of the main reasons a lot of people think they just need to "change their mind about the world" is because that IS a stepping stone toward the truth - but is not the final goal. It's just a way to get to where you stop protecting the illusion and are ready to dissolve the underlying thought of separation/attack-on-God which caused it to appear. And since the Course does speak to taking those steps toward undoing distorted perception, people get caught up thinking that's all they need to do, and that after that the 'real world' will be kept - the physical world. That's not what it means. There are steps after that where the world disappears because it as only ever an illusion in the mind.
I think also this has a lot to do with how people perceive themselves as a separate body. That's what we come to the course with. I'm separate from 'the world out there'. I have a mind 'in here' in my body which is separate from the world 'out there' so this is the only part of reality that I have control over. I can change 'my mind' in here to see what's 'out there' differently. But that's NOT the point.
The point is, the very IDEA that your mind is separate from the world is what has to be undone - the whole idea of 'I have a separate mind' that is separate from the world. Because if you don't see that, you'll just want to keep the world and stay in a body and remain a separate ego identity having its own perception. And the truth is, you can't HAVE correct perception if you are still separate because as the mind is HEALED it is healed by union and undoing separation and joining and sharing, which means you have to realize that the world is IN your mind and it/your body are just mind-stuff. And as mind-stuff, they are just illusions, not reality. So the whole world ITSELF is not real. This is a very fundamental Course concept.
Again "The world is false perception. It is born of error, and it has not left its source. It will remain no longer than the thought that gave it birth is cherished." - Jesus
Once we stop cherishing the thought (separation) which gave 'birth' to ERROR, which is the world (the form of error), it will REMAIN NO LONGER and will disappear. Forgiveness is meant to OVERLOOK error, ie overlook the world, to get to where perception is purified so that it can see the world for 'what it is', and what it is is an illusion. Forgiveness must look PAST the illusion otherwise it is not forgiveness. It overlooks the world and recognizes it is NOT really there, because it's just a figment of the imagination. In all its physical-ness and energy-ness and all of its 'life forms' and everything - it's all unreal. It is not reality at all. This is why the idea of "there is no world" is so threatening to ALL Course students (me too) - it implies the total non-existence of the ego self that they think they are.
So what's left, if there is no world and the world disappears?
God's Creation! God's Creation was hidden BY the world, and that was the world's only purpose. Once removed, we will be AWARE of God's Creation again - not conscious of it, not perceiving it, but AWARE of being it.
The world is just a giant mind-game.