In 380 CE, Christianity was effectively adopted as the official religion of the Roman empire, and as the Church’s power and influence grew, its relationship with the state became a disputed issue. One of the first political philosophers to address this question was Augustine of Hippo, a scholar and teacher who became a convert to Christianity. In his attempt to integrate classical philosophy into the religion, he was greatly influenced by his study of Plato, which also formed the basis for his political thinking.

As a Roman citizen, Augustine believed in the tradition of a state bound by the rule of law, but as a scholar, he agreed with Aristotle and Plato that the goal of the state was to enable its people to lead the good and virtuous life. For a Christian, this meant living by the divine laws prescribed by the Church. However, Augustine believed that, in practice, few men lived according to divine laws, and the vast majority lived in a state of sin. He distinguished between two kingdoms: the civitas Dei (city of God) and the civitas terrea (city of Earth). In the latter kingdom, sin predominates. Augustine sees the influence of the Church on the state as the only means to ensure that the laws of the land are made with reference to divine laws, allowing people to live in the civitas Dei. The presence of such just laws distinguishes a state from a band of robbers. Robbers and pirates join together under a leader to steal from their neighbors. The robbers may have rules, but they are not just rules. However, Augustine further points out that even in a sinful civitas terrea, the authority of the state can ensure order through the rule of law, and that order is something we all have a reason to want.

Just war

Augustine’s emphasis on justice, with its roots in Christian doctrine, also applied to the business of war. While he believed all war to be evil, and that to attack and plunder other states was unjust, he conceded that a “just war” fought for a just cause, such as defending the state against aggression, or to restore peace, did exist, though it should be embarked upon with regret and only as a last resort.

"Without justice an association of men in the bond of law cannot possibly continue."

Augustine

This conflict between secular and divine law, and the attempt to reconcile the two, began the power struggle between Church and state that ran through the Middle Ages.

Augustine’s vision of a state living according to Christian principles was outlined in his work City of God, in which he described the relationship between the Roman empire and God’s law.

AUGUSTINE OF HIPPO

Aurelius Augustine was born in Thagaste (now Souk-Ahras, Algeria) in Roman North Africa, to a pagan father and a Christian mother. He studied Latin literature in Madaurus and rhetoric in Carthage, where he came across the Persian Manichean religion, and became interested in philosophy through the works of Cicero. He taught in Thagaste and Carthage until 373, when he moved to Rome and Milan, and there was inspired by theologian Bishop Ambrose to explore Plato’s philosophy, and later to become a Christian. He was baptized in 387, and was ordained a priest in Thagaste in 391. He finally settled in Hippo (now Bone, Algeria), establishing a religious community and becoming its bishop in 396. As well as his autobiographical Confessions, he wrote a number of works on theology and philosophy. He died during a siege of Hippo by the Vandals in 430.

Key works

387–395 On Free Will

397–401 Confessions

413–425 City of God