Augustine's thinking was characterised by a close connection between philosophy and theology.

• Trinity doctrine: Augustine made an important contribution to the development of the Christian Trinity doctrine. In his work ‘De Trinitate’ (On the Trinity) he tried to explain and anchor the doctrine of the Trinity. Doctrine of Grace: The doctrine of grace of Paul of Tarsus was a central element in Augustine's theology. The City of God: In his work ‘De civitate Dei’ (On the City of God), Augustine developed an influential philosophy of state and history that deals with the relationship between the secular and divine order.

• Platonism and Christianity: Augustine played a decisive role in the reconciliation of the ideas of Greek philosophy, especially Platonism, with Christianity. Epistemology: He dealt intensively with questions of knowledge and understanding. Ethics and moral philosophy: Augustine developed influential ideas on questions of morality and right action.

• Bible interpretation: Augustine emphasised the necessity of a philosophical interpretation of the Bible and warned against taking the Bible literally. He promoted the allegorical interpretation of biblical texts.

• Concept of humanity: Augustine's ideas about humanity, especially in relation to sin, free will and salvation, had a formative influence on Christian anthropology.

• In his ‘Confessions’, Augustine combined personal experiences with theological reflections, creating an influential work of self-reflection.

Major works

Theological major works

1. ‘De civitate Dei’ (The City of God): An apologetic work in 22 books, written between 413 and 427.

2. ‘De Trinitate’ (On the Trinity): A dogmatic major work in 15 books dealing with the Christian doctrine of the Trinity.

3. ‘De doctrina christiana’ (On Christian Doctrine): A textbook in 4 books dealing with dogmatics and exegesis.

Philosophical works

1. ‘De ordine’ (On Order): A philosophical work in 2 books, written in Cassiciacum at the end of 386.

2. ‘Soliloquia’ (Soliloquies): Another philosophical work in 2 books, also written in Cassiciacum in the winter of 386-387.

Other major writings

1. ‘Retractationes’ (Retractions): In this work, Augustine critically reviewed his earlier writings.

2. ‘De libero arbitrio’ (On Free Will): An important treatise in 3 books.

3. ‘Epistulae’ (Letters): A collection of 246 extant letters, which represent only a fraction of his total correspondence.

4. ‘Sermones’ (sermons): 559 sermons have been preserved, with the total number of sermons he delivered estimated at between 4,000 and 8,000.

Influence

On medieval philosophers

Augustine's ideas had a significant impact on medieval philosophy. Particularly noteworthy are:

• Thomas Aquinas: Although he followed Aristotle, he integrated many Augustinian elements into his thinking.

• Anselm of Canterbury: His proofs of the existence of God were based on Augustine's ideas.

• Bonaventure: He represented a strongly Augustinian philosophy and theology.

On modern philosophers

• René Descartes: He saw Augustine as the forerunner of his famous ‘Cogito ergo sum’.

• Blaise Pascal: many of his philosophical ideas were inspired by Augustine.

• Nicolas Malebranche: his doctrine of ‘vision in God’ goes back to Augustine.

Modern philosophers

• John Henry Newman: his philosophy of religion shows clear Augustinian traits.

• Existential philosophers: Augustine's reflections on the self influenced existentialist thinkers.

Augustine thought that everything in the world was created by God. 

For Vico, history is limited in time, but it participates in a form of eternity through the immutable laws and principles that structure it and bring it closer to an eternal, divinely created order of providence.