The keys are an office and a power of the church, given by Christ, to bind and to loose sins, not only such as are gross and manifest, but also subtle and secret sins, which God alone perceives; as it is written in the 19th Psalm, verse 12: "Who can understand his errors?" And St. Paul, Rom. 7, 25, complains: "That with the flesh he serves the law of sin." For it does not lie within our power, but in that of God alone, to judge which are sins, and of their enormity and number; as it is written in the 143d Psalm, verse 2: "Enter not into judgment with thy servant: for in thy sight shall no man living be justified." And Paul, 1 Cor. 4, 4, also says: "For I know nothing by myself; yet am I not hereby justified."