"God did not make the body, because it is destructible, and therefore not of the Kingdom. The body is the symbol of WHAT YOU THINK YOU ARE. It is clearly a separation device, and therefore does not exist."
In ACIM, Jesus teaches in many ways that the body, the ego and the world are nothing. Even that they don't really exist at all in reality. But another major part of the teaching is that we've invested these things with meanings, laws, rules, values, powers, which they do not have.
"It cannot make a body, nor abide within a body. What is alien to the mind does not exist, because it has no source."
As a further step, Jesus goes on to say that if you give the body power or meanings or roles that it is not supposed to have, being nothing at all, this is what makes it sick. The body becomes sick because your mind is trying to distort it from being nothing into being something else. It is putting pressure onto the body, trying to manipulate it into serving made-up causes.
"You might ask how the voice of something which does not exist can be so insistent. Have you ever seriously considered the distorting power of something you WANT, even if it is not true?"
As Jesus says, if you believe that the body has an ability to create, meaning an ability to cause something, your mind will be sick and it will manifest this sickness upon/as/in the body. Since the body is nothing, it does not have an ability to cause anything. If you believe the body can or is causing something, your mind is sick, and this will make the body sick.
"The body cannot create, and the belief that it CAN, a fundamental error responsible for most of the fallacies already referred to, produces all physical symptoms."
The same applies to the world. It's easy to say we're not at the effect of the world, but we need to also realize we've invested the world will all kinds of powers, casual abilities, creative powers, trying to make it be something, with false values and credit where it's not due etc. And these things distort the world and effectively results in a sick mind, a sick body, and a sick projected world. The world has to be recognized as absolutely nothing, rather than believed to be something of importance.
"As "something", is the body asked to be God's enemy, replacing what He is with littleness and limit and despair. It is HIS loss you celebrate when you behold the body as a thing you love, or look upon it as a thing you hate. For if He be the sum of everything, then what is NOT in Him does not exist. And His completion IS its nothingness."
It may seem odd at first, but Jesus wants us to recognize that all bodies are nothing. They are not something. They are much closer to being emptiness and lack, being the idea of sin. We need to stop giving power to them, stop giving value to them, stop making them out to be something they're not, and stop trying to give them worth.
"The body, valueless and hardly worth the least defense, need merely be perceived as quite apart from you, and it becomes a healthy, serviceable instrument through which the mind can operate until its usefulness is over. Who would want to keep it when its usefulness is done?"
Jesus even says that they are so worthless as to be not even worth defending, and that if you defend the body you will make it sick. By this worthlessness he does not mean that the body is judged as evil or that we project guilt onto it or make it out to be a victim or a perpetrator. It doesn't mean we value it as low and hated and so on. He simply means that because it is neutral it is nothing, and its neutrality means that you cannot give it any attributes at all, either positive or negative.
"As nothing, which it IS, the body cannot meaningfully be invested with attributes of Christ OR of the ego. EITHER must be an error, for both would place the attributes where they cannot BE."
The body is essentially not there. It is not real. It does not exist. It's an hallucination, empty, void, pretending to show up as something but isn't even a real creation.
"At no SINGLE instant does the body exist at all. It is always remembered or anticipated, but NEVER experienced just now. Only its past and future make it seem real. Time controls it entirely. For sin is never present."
Jesus goes on to suggest that if you can recognize the body as nothing at all, withdrawing all artificial beliefs, uses, roles, laws, meanings and so on from it, the body will actually become a picture of health. The reason is that the mind is becoming "clear" and empty of illusions, and therefore the picture of the body begins to fade and disappear, at first infused with light and healing and love, but eventually eradicated by it.
From the state of a healthy mind and body, the body will go on to disappear entirely into the light, consumed by it and erased by it. Recognizing your brother's body as nothing is the way for your body to be free from sickness and death. Regarding a person as a body is a form of separation-belief, and so is an attempt to be split off from life. Your brother's body, your spouse's body, your children's bodies, your neighbor's bodies, they are all absolutely nothing and worth nothing all. Mistaking these people for their bodies is an attack upon who they really are.
"His body's nothingness releases yours from sickness and from death. For what is yours cannot be more NOR less than what is his."
"Perhaps you do not realize that this removes the limits you had placed upon the body by the purposes you gave to it. As these are laid aside, the strength the body has will always be enough to serve all truly useful purposes. The body's health is fully guaranteed because it is not limited by time, by weather or fatigue, by food and drink, or any laws you made it serve before. You need do nothing now to make it well, for sickness has become impossible."
Finally, Jesus suggests that if you take this all the way, if you deprogram your mind from belief that the body and the world and the ego are ANYTHING, and recognize them as nothing at all, they will disappear. What is recognized as nothing cannot really be there, and this causes it to not be there. In truth, there is no body, there is no ego, and there is no world.
"To roll the stone away is to see beyond the tomb, beyond death, and to understand the body's nothingness. What is understood as nothing must disappear."
We are tasked with nothing short of erasing the world, ending space and time, and returning to the complete recognition that they are not there, they never were there, and only God's Kingdom really exists.
"What seems to be the opposite of life is merely sleeping. When the mind elects to be what it is not, and to assume an alien power which it does not have, a foreign state it cannot enter, or a false condition not within its Source, it merely seems to go to sleep a while. It dreams of time; an interval in which what seems to happen never has occurred, the changes wrought are substanceless, and all events are nowhere. When the mind awakes, it but continues as it always was."