Being separated in bodies, we have become accustomed to seeing ourselves as CONFINED. As though completely fenced in.
But this is utterly UNLIKE the way we really are.
It is far more accurate to say, you are everywhere, and in all people, and share everything with everyone. You overlap them, merge with them, join with them, part of you is in them and they in you. This is your natural state.
Bodies were made to isolate you and confine you and separate you off from the parts of you which are IN your brothers, to make it seem as though you have been disallowed to connect, join, communicate, or love each other.
The body is the idea of sin or separation. "The body is the idea of sin made flesh and projected outwards".
When studying ACIM then, from Jesus's perpsective, your true nature is that you are not confined to your body, you are unlimited, you are everywhere and in everyone, you share everything and literally are inside of other people.
In that context, you can better understand why he says so many things about the Golden Rule applying, about what you do to your brother being done to you, how you cannot attack without attacking yourself, how recognizing your brother's truth recognizes your own etc.
All healing therefore is actually the undoing of CONFINEMENT and ISOLATION, restoring the CONNECTION and COMMUNICATION with your brother, lifting away the separations that have been put in place BY BODIES to split you off from others, and restoring the wholeness and unity that is natural to you.
Health IS oneness with your brother. Healing IS the repair of the RELATIONSHIP between both of you. Separation and blocks to awareness do not just apply to YOU, they apply BETWEEN you and your brother. Your sickness is an attack on BOTH of you.
Just because you have BECOME ISOLATED by the separation idea, you think that in your confinement, anything the course is saying applies to your CONFINED SELF. As though it speaks only of your isolated "self' that is inside your body. IT DOES NOT. It is recognizing that you share fully with all brothers and that in your NATURAL condition you are everywhere and one with all people, actually literally IN THEM. And therefore, the idea of separation is not just something "inside" your mind, it is what MAKES YOU ISOLATED from others.
Holy relationships are therefore completely natural. They do not just mean two *separate* people being holy toward each other. They actually mean two individuals who have FULLY JOINED AND MERGED MINDS and are essentially sharing the same space! You are in your brother and your brother is in you. "One mind contains all minds. One brother is all brothers." You overlap with your brother and join with and share with them like a FUSION of individuals.
It's far more effective then to realize that every form of separation, every block to awareness, every form of sickness, every way you isolate or are in denial, is not simply something you "do to yourself', it is something you do TO BOTH OF YOU, IN-BETWEEN the two of you. Your bodies were made to imprison you AWAY from each other, and being set free from that imprisonment doesn't mean you remain NON-SHARING, it means you return TO OVERLAPPING WITH EACH OTHER, beyond the bodies.
The body when used as a communication device is therefore completely overlooked, it's form or attempted isolation is turned into a holy temple, and the light in your mind shines PAST it directly PAST the body of your brother and extends INTO their mind. Communication is direct mind-to-mind or soul-to-soul sharing. This produces the ERASING of separation and therefore the reversal of all sickness and death.
This is why Jesus says "no-one returns to God alone". You return to TOGETHERNESS. Unity. Sharing. Oneness. Mutual holiness. Joined minds. Shared interests. Overlapping experience. Equality. Blending into your brother as though they are yourself. Sharing space with all brothers. Collapsing separation and collapsing spacetime.