Since the world does not contain any real causes, and absolutely everything is an affect of the mind on a higher level, this shines some light on what happens when you are attacked or hurt.
If it seems that someone comes along and hits you, and a bruise forms, this is an illusion.
The person hitting and the formation of the bruise are not actually connected by any kind of linear causality. Laws of physics DO NOT EXPLAIN how the bruise gets there.
The bruise does not show up as a result of the attack.
The bruise shows up because your own mind buys into the illusion of linear cause and effect, and USES the opportunity to demonstrate that the other person is the "cause" of your hurt. This is an attempt to demonstrate that you can be hurt, in order to prove your brother is a sinner, so that you can get rid of your sin!
Your own mind puts the bruise in your own body, all by itself. It doesn't get there by the "causal power" of another person. If you believe in the causal power of another person, what your mind is doing is it is actually twisting itself so that it can seem to attack itself from the outside in, through that person, and it is your mind which puts the bruise there.
This works in exactly the same way to how medication works, which is that you pretend that something outside of you will do something to you, your MIND decides whether or not to allow it, and IF it allows it, the MIND ITSELF puts the effects into the body, not the medication. All medication is a placebo. None of it has power to cause anything but illusions.
If the mind decides not to get well, IT WILL REFUSE the illusion of the medication and the medication will NOT WORK. Similarly, among those who refuse to believe in the cause-effect of certain foods, they can eat those foods WITHOUT EFFECT even if they would hurt other people. Mind over matter!
Jesus asks us in the Course to demonstrate that we cannot be hurt, or attacked, or sick, and that our brother is innocent because nothing they try to do us produces ANY EFFECTS.
If we produce sickness in the body after eating the wrong food, or we develop a bruise after being hit, or we walk around with a broken leg due to falling out of a tree, we are ACCUSING everyone else (ie the world) of doing this to us.
This means we are attempting to prove that we CAN BE HURT. This proof demonstrates for all to see, that someone else must be the sinner, because something happened that you *appear* to not want to have happened, against your will. Your demonstration of "being a victim" is actually a show that your mind puts on, for a purpose, to scapegoat the world.
What Jesus is therefore asking is, that we become invulnerable to attack, incapable of being sick, unable to be hurt, and that we refuse to CHOOSE to show up as damaged or broken. This means that when it SEEMS in the illusion that there is a linear causality of someone hitting you, YOU DO NOT develop a bruise. When you fall out of the tree, you DO NOT break your leg. When you eat a certain food, IT DOES NOT poison you.
This means you are supposed to get to where you can SUPERNATURALLY DEMONSTRATE that you cannot be hurt, sick, damaged, or made to suffer, in any way, by any cause in the entire world! At the physical level! He is asking us to show that we are holy by showing that the Son of God CANNOT BE DESTROYED, using the body as a SYMBOL of immortality.
Here is how Jesus puts it:
"It is your thoughts alone that cause you pain. NOTHING EXTERNAL TO YOUR MIND CAN HURT OR INJURE YOU IN ANY WAY. There is no cause beyond yourself that can reach down and bring oppression. NO ONE BUT YOURSELF AFFECTS YOU. There is nothing in the world that has the power to make you ill or sad, or weak or frail." !!!!!!!
He also speaks of this here:
"Sickness is an attempt to demonstrate that you can be hurt"
"A broken body proves the mind has not been healed"
"The central lesson is always this; that what you use the body for it will become to you. Use if for sin or for attack, which is the same as sin, and you will see it as sinful. Because it is sinful it is weak, and being weak, it suffers and it dies. Use it to bring the Word of God to those who have it not, and the body becomes holy. Because it is holy it cannot be sick, nor can it die."
"(regarding your brother) But every pain you suffer do you see as proof that he is guilty of attack. Thus would you make yourself (your body) to be the sign that he has lost his innocence, and need but look on you (your body) to realize that he has been condemned. And what to you has been unfair will come to him in righteousness. The unjust vengeance that you suffer now belongs to him, and when it rests on him are you set free (you projected your sin). Wish not to make yourself a living symbol of his guilt, for you will not escape the death you made for him."
Here Jesus is basically saying that you must not attempt to put sin and death onto your brother through attack of any kind (sickness also) because if you do, YOU will be attacked. This is the basic law of the one mind, that what you do to your brother you to do yourself. All attack is self attack. You cannot escape the consequences of your attempted attack on another, and they are not required to receive those consequences from you.
This means that if you demonstrate that you are sick or hurt physically IN ANY WAY, you are attacking your brother, trying to SHOW HIM what he must have done to you against your will, and are therefore projecting your sin! If you do this, you will suffer, and your will experience death. This also means YOUR MIND *IS NOT HEALED*, therefore you CANNOT experience peace. A broken body proves your mind is not healed. Your mind is proven to be healed when your body shows up as NOT BROKEN. Therefore, to escape death, you MUST NOT use the body for attack, thus rendering it INCAPABLE of being attacked by you or anyone.
Whenever you attempt to use the body for attack, which means, to fail to extend love through it to your brother, the body itself will become sick. The sickness in your body will directly correlate to your belief that you and your brother are sinners. Your attempt to project your sin will project it onto your body and destroy it. This is the ONLY WAY that bodies become sick. Not through external causes, not through the illusion of cause and effect, not through your brother.
We are therefore REQUIRED, and WILL NOT BE ABLE TO AVOID, to demonstrate that our body is absolutely invulnerable, in order to CANCEL OUT the illusion of cause and effect, to PROVE that the ego's laws mean nothing, to SHOW that our brother is as innocent as we are, and to TEACH that the Son of God cannot be hurt or affected by illusions in any way.
Can you imagine what a miracle it will be to witness someone demonstrating this? That nothing you try to do to them works? That you cannot hurt their body whatsoever? That their body cannot even die no matter how you try to attack it? Their mind will simply project an image of permanent health the whole time, IGNORING anything you try to do to it. And by this will be PROVEN your innocence, because no sin you try to commit WORKS, and therefore you CANNOT believe that you are sinful. Thus are you set free because your attempted sin HAD NO CONSEQUENCES. This is how you set your brother free from his belief that he sinned!
This is one of the most radical teachings in the course, so I understand that many people don't believe this or don't want to. But this is what Jesus has said. If your body is broken in any way, you are teaching vulnerability and suffering and sin. You cannot have sickness in the body and prove that you are innocent, or to be at peace. And you cannot be at peace with death. You cannot have sickness showing up if you want to be awake, and being awake you WILL NOT show sickness to anyone. The body MUST HEAL if the mind heals. And the body will become as immortal as the mind.
Cause and effect at the level of the world is entirely an illusion. THERE IS NO CAUSE in the world. Nothing causes you. Nothing is the reason why you are showing up in any particular form. Nothing has happened to you against your will. Nothing of this world can be found responsible for having power over you, for "making you" be a certain way, for instigating illness, to triggering suffering, or for making your body change in any way at all. Not even the forces of nature or acts of nature or whatever else. NOTHING.
Your body is 100% a projected image from YOUR MIND, and YOU are the one that determines how it is going to show up. Not this world. Not other people. Not food or water or weather or anything else. We are meant to demonstrate that our body is completely invulnerable, completely NOT DEPENDENT on anything of this world, and incapable of being affected by this world. This will demonstrate the the mind of love has power over all illusions and nothing can assail the Kingdom of God.
If we're sick, hurt, in pain, suffering, a victim, abused, damaged, missing something, lacking, attacked, upset, whatever... we are the ones who are putting it there, we are RESPONSIBLE for it, and no-one else has caused it. Only through this willingness to admit honestly to this truth, will you be able to access the SUPERNATURAL PROTECTION which comes from realizing the secret to salvation: "you are doing this to yourself". If you stop doing it to yourself, NOTHING ELSE WILL BE ABLE TO DO ANYTHING TO YOU.
I'll let Jesus finish up with this section from "sickness is a defense against the truth":
"The body should not feel at all. If you have been successful, there will be no sense of feeling ill or feeling well, of pain or pleasure. No response at all is in the mind to what the body does. Its usefulness remains and nothing more.
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**.
Yet this protection needs to be preserved by careful watching. If you let your mind harbor attack thoughts, yield to judgment or make plans against uncertainties to come, you have again misplaced yourself, and made a bodily identity which will attack the body, for the mind is sick."