So what is the lesson? What does Atonement really mean? Let's look at the beginning of Chapter 13, which is called "The Guiltless World":
"If you did not feel guilty you could not attack, for condemnation is the root of attack. It is the judgment of one mind by another as unworthy of love and deserving of punishment. But herein lies the split. For the mind that judges perceives itself as separate from the mind being judged, believing that by punishing another, it will escape punishment. All this is but the delusional attempt of the mind to deny itself, and escape the penalty of denial. It is not an attempt to relinquish denial, but to hold on to it. For it is guilt that has obscured the Father to you, and it is guilt that has driven you insane.
The acceptance of guilt into the mind of God's Son was the beginning of the separation, as the acceptance of the Atonement is its end. The world you see is the delusional system of those made mad by guilt. Look carefully at this world, and you will realize that this is so. For this world is the symbol of punishment, and all the laws that seem to govern it are the laws of death. Children are born into it through pain and in pain. Their growth is attended by suffering, and they learn of sorrow and separation and death. Their minds seem to be trapped in their brain, and its powers to decline if their bodies are hurt. They seem to love, yet they desert and are deserted. They appear to lose what they love, perhaps the most insane belief of all. And their bodies wither and gasp and are laid in the ground, and are no more. Not one of them but has thought that God is cruel.
If this were the real world, God would be cruel. For no Father could subject His children to this as the price of salvation and be loving. Love does not kill to save. If it did, attack would be salvation, and this is the ego's interpretation, not God's. Only the world of guilt could demand this, for only the guilty could conceive of it. Adam's "sin" could have touched no one, had he not believed it was the Father Who drove him out of paradise. For in that belief the knowledge of the Father was lost, since only those who do not understand Him could believe it.
This world is a picture of the crucifixion of God's Son. And until you realize that God's Son cannot be crucified, this is the world you will see. Yet you will not realize this until you accept the eternal fact that God's Son is not guilty. He deserves only love because he has given only love. He cannot be condemned because he has never condemned. The Atonement is the final lesson he need learn, for it teaches him that, never having sinned, he has no need of salvation."
In reality you have no need of a savior, of salvation. Yet here, in space time, you do not know who you are, where you are from, and what it is you do. You cannot solve your problem, because you do not recognize what it is. You cannot do anything. You absolutely need help. That is why you have A Course In Miracles, Jesus, the Holy Spirit, Master Teacher and all your brothers who share your goal of remembering who you are, for there is only you, only your mind to wake up from this nightmare of crucifixion. Train your mind to recognize that this is all solved, over and gone. A Course In Miracles provides you with the means of a mind training to become miracle-minded and let go of this world of illusion. There is nothing the miracle cannot do for you in your desire to awaken to your reality.
It is a miracle... It is the Search for Jesus. He is back with you.