St. Augustine (354–430) tried to justify the whole of human knowledge, even though he also allowed for error. All knowledge, according to Augustine, resided within the soul as “a substance endowed with reason and fitted to rule a body.” While the soul can act on the body, the body cannot act on the soul. God is always present to the soul, whether the soul is aware of his light or turns away from it. These views of Augustine established the superiority of religion to philosophy and also embedded God in the same human faculty associated with non-religious understanding to the elevation of religious understanding.

Augustine’s greatest work was The City of God, in which he separated the temporal state (government on Earth) from the religious realm of the afterlife. The temporal state was to have a secondary role in ensuring peace, order, safety, and physical well being for its citizens. The heavenly city, by contrast, requires living according to God’s rules. Although the temporal and heavenly cities may at times overlap, only God’s city is eternal.