Book V.
The knowledge of the nature of God, and faith, and right affections towards Him, are the sum and true foundation of all good; for what the eye is to the body, that faith and the knowledge of divine matters are to the soul. But then she needs also at the same time practical virtue, as the eye does hands and feet, and the other members of the body.
Wherefore, the holy apostle adds moral instructions also to his doctrinal course, in order to promote in us the most perfect virtue, for through the Romans does he afford this advantage to all mankind: and thus he opens the subject.