Introductory text prior to lesson 221 in the ACIM workbook - one of the Course's masterpieces on Forgiveness:
"What is Forgiveness?
Forgiveness recognizes what you thought your brother did to you has not occurred. It does not pardon sins and make them real. It sees there was no sin. And in that view are all your sins forgiven. What is sin, except a false idea about God's Son? Forgiveness merely sees its falsity, and therefore lets it go. What then is free to take its place is now the Will of God.
An unforgiving thought is one which makes a judgment that it will not raise to doubt, although it is not true. The mind is closed, and will not be released. The thought protects projection, tightening its chains, so that distortions are more veiled and more obscure; less easily accessible to doubt, and further kept from reason. What can come between a fixed projection and the aim that it has chosen as its wanted goal?
An unforgiving thought does many things. In frantic action it pursues its goal, twisting and overturning what it sees as interfering with its chosen path. Distortion is its purpose, and the means by which it would accomplish it as well. It sets about its furious attempts to smash reality, without concern for anything that would appear to pose a contradiction to its point of view.
Forgiveness, on the other hand, is still, and quietly does nothing. It offends no aspect of reality, nor seeks to twist it to appearances it likes. It merely looks, and waits, and judges not. He who would not forgive must judge, for he must justify his failure to forgive. But he who would forgive himself must learn to welcome truth exactly as it is.
Do nothing, then, and let forgiveness show you what to do, through Him Who is your Guide, your Savior and Protector, strong in hope, and certain of your ultimate success. He has forgiven you already, for such is His function, given Him by God. Now must you share His function, and forgive whom He has saved, whose sinlessness He sees, and whom He honors as the Son of God."