The association of Augustine with Neo-Platonism was important to both the possibility and the actuality of his conversion to the Christian faith.
In Milan when Augustine lived there, besides Epicureans, Cynics, Stoics and Sceptics (Augustine briefly became a Sceptic), there were still Aristotelians, generally called Peripatetics, and various Platonists, generally called Academics.
The Academic school became sceptical, and a breakaway group who rejected scepticism and who wanted to revive the doctrines of Plato called themselves the Old Academy.
In fact their doctrine was not pure Plato but a combination of Plato with parts of Aristotle.
Later there developed a school of Platonists which scholars now describe as Neo-Platonism. It combined the doctrines of Plato with some of those of Aristotle.
Neo-Platonism is considered the last of the great pagan philosophies. It was developed by Plotinus (205 - 270) in the century before the birth of Augustine.
Plotinus lived a simple and isolated life, and refused to give formal philosophical lectures.
It was his disciple Porphyry who revised the brief written notes of Plotinus. He organised them into groups of nine, hence they are called the Enneads.
Augustine recognised Neo-Platonism as the closest pagan philosophy to the beliefs of Christians.
This was mainly because its followers were not materialists as Epicureans and Stoics were, but held that there are immaterial or spiritual realities.
Ambrose, the Bishop of Milan, in his preaching gave Augustine exposure to the allegorical and Platonising interpretation of the Scriptures.
To the fascination and satisfaction of Augustine, the scholarly Ambrose presented his faith as a radically other-worldly Neo-Platonic philosophy.
This impressed Augustine, who had not been impressed by the literal interpretation of Scripture that had been practised by his mother, Monica.
Augustine was awakened to the philosophical life by reading Cicero, but the Neoplatonists most decisively shaped his philosophical methods and ideas.
To them he owed his conviction that beyond the world of the senses there is a spiritual world.
Augustine began serious study of Neo-Platonism in Milan soon after he first met Ambrose. This reading may have included writings by Plotinus (205 - 270) himself.
As Plotinus wrote in Greek, however, Augustine possibly relied on Latin translations because he did not read the Greek language very easily himself.