The Influence of St. Augustine and St. Thomas Aquinas on Political Thought

Between the fall of Rome and the rebirth of classical learning in medieval Europe, two thinkers shaped how the West would understand power, law, and the relationship between earthly rulers and divine authority. St. Augustine of Hippo and St. Thomas Aquinas lived more than eight centuries apart, yet together they form the backbone of medieval political thought. Augustine wrote as a Roman world was crumbling around him, while Aquinas wrote at the height of medieval Christendom when Greek philosophy was flooding back into Europe. Understanding these two figures is essential for grasping how religion and politics became intertwined, and how ideas about justice, law, and the state developed long before modern democracy.

St. Augustine and the crisis of a falling empire
The doctrine of the two cities
Augustine’s view of the state
St. Thomas Aquinas and the grand synthesis
A more optimistic view of the state
The four types of law
Natural law and its lasting reach
Church and state: continuity and contrast
The just war tradition
Why these thinkers still matter

St. Augustine and the crisis of a falling empire

St. Augustine (354-430) lived during one of history’s most turbulent periods. When the Visigoths sacked Rome in 410 AD, the shock rippled across the ancient world. Many Romans blamed Christianity, arguing that abandoning the old pagan gods had left the empire defenceless. Augustine, then the Bishop of Hippo in North Africa, took up the challenge of responding to these accusations. His answer became one of the most influential works in Western political thought.

That work was The City of God (De Civitate Dei), written between roughly 413 and 426 AD. Rather than simply defending Christianity, Augustine reframed the entire question. He argued that Rome’s fall was not the collapse of God’s kingdom, because God’s kingdom had never been Roman in the first place. With this single move, he separated political power from divine authority, a connection that had dominated ancient thought.

The doctrine of the two cities

At the heart of Augustine’s political theory lies the division of all humanity into two “cities.” These are not actual places or institutions but rather two communities defined by what they love. As Augustine put it, two cities were formed by two loves: the earthly city by love of self, and the heavenly city by love of God.

The two cities can be understood through their defining features:

The City of God (Civitas Dei): Made up of those who live according to God’s design, motivated by love of God and the pursuit of eternal peace. Its citizens look toward salvation and everlasting life rather than worldly gain.

The Earthly City (Civitas Terrena): Made up of those who live according to themselves, driven by self-interest, the desire for power, and pride. This city seeks temporal goods and is marked by conflict and competition.

It is important to understand that for Augustine, the distinction was not the same as separating the Church from the state. The two cities are spiritual orientations rather than geographic societies, and their members are mixed together in the world until the final judgment. Both cities even desire peace, but the earthly city wants peace to enjoy material goods, while the heavenly city seeks eternal peace with God.

Augustine’s view of the state

Augustine held a notably pessimistic view of earthly government. Because of original sin and human fallenness, he saw the state largely as a remedy for sin, a necessary instrument to maintain order in a corrupt world. Government, with its coercion and punishment, exists to restrain human wickedness rather than to perfect human virtue. This was a sharp departure from the Greek view of Plato and Aristotle, who believed that a good life could be achieved within a well-organized city-state. Augustine no longer assumed that fulfilment was possible through politics alone; he projected human destiny into a cosmic drama working toward a predetermined end.

St. Thomas Aquinas and the grand synthesis

Eight centuries later, the intellectual climate had transformed completely. St. Thomas Aquinas (1224/25-1274) was a Dominican friar who lived during the climax of medieval civilization. By his time, the works of Aristotle had been reintroduced to Europe, largely through translations that arrived via Arabic sources. This created a crisis in Christian circles: how could the church reconcile Aristotelian philosophy, which relied heavily on human reason, with a faith built on divine revelation?

Aquinas’s genius was to resolve this tension. In his masterwork, the Summa Theologica, he created what scholars often call the “grand synthesis,” merging Aristotelian philosophy with Christian theology. He argued that faith and reason were not enemies but partners. Some truths could be reached by human reason alone, while others required divine revelation, and the two complemented rather than contradicted each other.

A more optimistic view of the state

This synthesis led Aquinas to a view of politics very different from Augustine’s. Where Augustine saw the state as a remedy for sin, Aquinas followed Aristotle in viewing humans as naturally political beings who require organized society. For Aquinas, the state was not merely a consequence of human sinfulness but a natural necessity arising from our social nature. A scholarly comparison of the two thinkers notes that while Augustine views the state as a remedy for sin, Aquinas sees it as a natural necessity for social beings.

This meant government had a positive purpose. A just ruler, Aquinas argued, must work for the common good of all citizens rather than personal interests. He famously defined law itself as an ordinance of reason directed toward the common good, made by the one who has care of the community, and properly made known to the people.

The four types of law

Perhaps Aquinas’s most enduring contribution to political and legal thought is his classification of law into four interconnected types. This framework grounded all legitimate authority in a rational, divine order.

Eternal Law: The divine reason and providence by which God governs the entire universe. This is the foundation from which all other laws derive.

Natural Law: The participation of rational creatures in the eternal law. Through reason, humans can decide between good and evil. Its first principle, according to Aquinas, is that good is to be done and pursued, and evil is to be avoided.

Human Law: The specific rules and statutes that societies create by applying natural law to particular circumstances. When human law contradicts natural law, Aquinas argued, it loses its true character as law.

Divine Law: The law revealed through scripture, which guides humanity toward its ultimate spiritual end of union with God, addressing matters that human reason alone cannot reach.

Natural law and its lasting reach

Aquinas’s theory of natural law has proven remarkably durable. He held that moral principles are accessible to human reason and binding on all people, regardless of their religion or culture. Because these principles are universal, they provided a powerful basis for arguing that rulers are accountable to a higher standard than their own will. The Stanford Encyclopedia of Philosophy notes that Aquinas tied the principles of practical reason not to individual happiness alone but to the flourishing of the whole community. These ideas later influenced Enlightenment thinkers and continue to inform modern debates about human rights and the limits of government power.

Church and state: continuity and contrast

Both thinkers grappled with the central political question of their age: the relationship between spiritual and temporal authority. Medieval thought was often characterised by the “doctrine of the two swords,” in which one sword symbolised the secular ruler and the other the Church. In an era when the Church was the dominant institution, its decisions in matters of faith were treated as final.

Despite their different starting points, both Augustine and Aquinas agreed that the Church held the higher goal of human salvation while the state was tasked with promoting moral life and maintaining order. They envisioned a cooperative relationship between the two institutions, even if they disagreed on the precise balance of authority.

The just war tradition

A concrete example of their combined influence is just war theory. Augustine laid the early foundations, arguing that a just war required legitimate authority, a just cause, and right intention, meaning a disposition toward restoring peace rather than conquest. Aquinas later refined and systematised these ideas. He restated the conditions for a just war and, reflecting his Aristotelian framework, grounded the ruler’s war-making authority less in direct divine command and more in the king’s role as guardian of the kingdom. This tradition continues to shape international law and ethical debates about armed conflict today.

Why these thinkers still matter

The contrast between Augustine and Aquinas captures a fundamental tension in political thought. Augustine emphasised human imperfection, the limits of earthly politics, and the priority of spiritual salvation. Aquinas, drawing on Aristotle, offered a more confident vision in which reason could discover moral truth and politics could serve genuine human flourishing. Together, they shaped the medieval understanding of law, the state, and the relationship between religion and political power.

Their ideas did not stay confined to the Middle Ages. Aquinas’s natural law theory influenced later philosophers and even contributed to modern concepts of rights and resistance against unjust rulers. Augustine’s separation of divine authority from any single political order helped create intellectual space for distinguishing the religious from the secular. In a world where questions about the role of religion in public life, the meaning of justice, and the foundations of law remain very much alive, both thinkers continue to offer insight.

What do you think? Does Augustine’s view of the state as a remedy for human sinfulness or Aquinas’s view of it as a natural and good institution better describe the governments we live under today? And in an age of written constitutions, is there still room for the idea of a “natural law” that stands above the laws passed by any parliament?

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Table of Contents

St. Augustine and the crisis of a falling empire 🔗

The doctrine of the two cities 🔗

Augustine’s view of the state 🔗

St. Thomas Aquinas and the grand synthesis 🔗

A more optimistic view of the state 🔗

The four types of law 🔗

Natural law and its lasting reach 🔗

Church and state: continuity and contrast 🔗

The just war tradition 🔗

Why these thinkers still matter 🔗