All thoughts create form at some level. This is because thoughts (ego thoughts) are ideas about separation. Regardless of their specific content they are always separation ideas.
Separation ideas always therefore lead to "form" in some way.
What this means is, the idea of separation from God, having that tiny mad idea, AUTOMATICALLY means that form MUST come from it. Form must be the end result of an idea of separation. The thought ITSELF shows up as form - separate images appearing real, and eventually being so "firm" that they seem like solid matter.
Form results from thoughts of separation because separation requires us to make an illusion of how two things are different and disconnected, not sharing space or properties. These illusory appearances make it seem like separation is real and result in the illusion of "separate objects".
Any ego thought therefore emphasizes separation between illusions. As the division between thoughts intensifies, or becomes more "dense", it HAS to eventually lead to the illusory manifestation of what we would call "physical solid matter" - a physical universe - which is essentially just a very heavy/serious thought.
Or to put it simply, the mad idea of being separate from God HAD to create a physical universe. It is a completely logical progression and consequence of having such an idea. Form derives from separation.
If separation is perceived or believed to be real, some kind of universe of forms, to some degree, must seem to manifest.
Before the physical universe there were also prior "stages" if you will, subtler levels of this, which have produced additional levels in the dream. Other dimensions. These are all part of the same ego holographic dream and many of these levels feature form to varying degrees.
As Jesus says for example, nighttime and waking dreams differ only in their forms/content. Being in the physical world is nothing more than being inside the tiny mad idea of separation. It is just an idea, and is not really happening. This is why the physical universe is an illusion. It's an illusory thought of separation - a thought of impossibility.
When you can recognize the illusion correctly, you have completed forgiveness. This means being able to transcend and overlook the thought which has made the physical world. Seeing the truth of this, is seeing the "real world", ie the true nature of the worlds of form (which may pertain to physical level as well as higher levels/dimensions of form).
Overlooking illusions makes them disappear. Overlooking the thought of separation makes it, and everything which has come from it (is inside it), disappear. This is why the physical and other higher dimensional universes MUST eventually disappear, or rather be recognized as having been nothing more than a dream/illusion to begin with. Illusions recognized must disappear. The tiny mad idea, recognized as purely false, must end.
Only Heaven is reality, the home of Immortal Spirit. Only Heaven will be left when all of these illusory universes disappear. Only Heaven is the Home of God and the Son of God. Only Heaven, God's Creation, is the real truth - the real universe of oneness.