Letter 1016: As, when one who walks through devious ways takes anew the right path, the Lord embraces him with all eagerness, so afterwards, when one deserts the way of truth, He is more saddened with grief for him than He rejoiced over him with joy when he turned from error; since it is a less degree of sin not to know the truth than not to abide in it when...

Book I, Letter 16 To Severus, Bishop of Aquileia [a major city in northeastern Italy, near the Lombard frontier]. Gregory to Severus. When someone who has strayed from the path returns to the right road, the Lord embraces him eagerly. But when someone later abandons the truth, God is more grieved by his departure than He rejoiced at his return -- because it is a lesser sin not to know the truth than to know it and fail to live by it. What is done in ignorance is one thing; what is done knowingly is another. We who formerly rejoiced at your incorporation into the unity of the Church are now all the more deeply distressed by your separation from Catholic fellowship [Severus and several bishops in the Aquileia region had broken communion with Rome over a theological dispute known as the Three Chapters controversy]. We therefore direct you, at the urging of the bearer of this letter and by command of the most Christian and serene Emperor [Mauricius], to come with your supporters to the threshold of the blessed Apostle Peter [to Rome]. There, God willing, a synod [formal church council] will be assembled to render judgment on the dispute among you.

Book I, Letter 16 To Severus, Bishop of Aquileia. Gregory to Severus, etc. As, when one who walks through devious ways takes anew the right path, the Lord embraces him with all eagerness, so afterwards, when one deserts the way of truth, He is more saddened with grief for him than He rejoiced over him with joy when he turned from error; since it is a less degree of sin not to know the truth than not to abide in it when known: and what is committed in error is one thing, but what is perpetrated knowingly is another. And we, from having formerly rejoiced in your being incorporated in the unity of the Church, are now the more abundantly distressed for your dissociation from the Catholic society. Accordingly we desire you, at the instance of the bearer of these presents, according to the command of the most Christian and most serene Emperor, to come with your adherents to the threshold of the blessed Apostle Peter, that, a synod being assembled by the will of God, judgment may be passed concerning the doubt that is entertained among you.