Sin is one of the core ideas from Christianity that A Course in Miracles revises. In traditional Christianity, a sin was an offense against God and nature for which one was punished, unless they repented. In A Course in Miracles, a sin is reframed as an error that can be corrected and its effects gently undone. It is not a cause for condemnation or punishment. Finally, the only actual “error” is the belief that we are separated from God. Thus, all error – and all the effects of error – are illusions. This is the foundation of salvation.