A Course in miracles Topic - Sin

 Sin is the world made real. The ego's triumph over God. Mistakes made uncorrectable.

  ... the ego made its world on sin. Only in such a world could everything be upside down. ... For sin has changed creation from an idea of God to an ideal the ego wants; a world it rules, made up of bodies, mindless and capable of complete corruption and decay. If this is a mistake, it can be undone easily by truth. Any mistake can be corrected, if truth be left to judge it. ... As a mistake, it must be brought to truth. ... a mistake can be corrected.  

    There is no stone in all the ego's embattled citadel that is more heavily defended than the idea that sin is real; ... .      T-19.II./6:7:1,2,5-7,11,13.

The betrayal of the Son of God lies only in illusions, and all his "sins" are but his own imagining. His reality is forever sinless. He need not be forgiven but awakened. In his dreams he has betrayed himself, his brothers and his God. Yet what is done in dreams has not been really done.              T-17.I.1:1-5.

 Sin is an idea of evil that cannot be corrected, and yet will be forever desirable.   T-19.III.1:6.

When you are tempted to believe that sin is real, remember this: If sin is real, both God and you are not. ... If sin is real, God must be at war with Himself. He must be split, and torn between good and evil; partly sane and partially insane. For He must have created what wills to destroy Him, and has the power to do so. ...                                                                      While you believe that your reality or your brother's is bounded by a body, you will believe in sin.                               T-19.III.6:1,3-5/7:1.