In Alexandria in the early 230s, a man of twenty-eight went from one philosophy lecture to the next and found nothing he wanted. A friend then took him to hear Ammonius Saccas, a self-taught Platonist who never wrote anything down, and Plotinus knew at once that he had found his teacher. He stayed eleven years. He and two fellow pupils, Erennius and Origen, agreed to keep what Ammonius taught among themselves. The other two broke the agreement; Plotinus kept it, and for his first ten years as a teacher in Rome he wrote nothing.
The claim he finally put into writing, from about 253, is this: everything that exists comes from a single source so simple that nothing true can be said of it. He called the source the One. It overflows, and what it produces first is Intellect, a mind whose thoughts are the patterns of all things. Intellect in turn produces Soul, which gives life and order to the visible world. Matter lies at the far end, where the outflow runs out; for Plotinus it is a lack rather than a thing, and the root of evil. The human soul lives in a body, but its highest part never comes down from Intellect, the world nearest the One; a life's work is to turn inward and recover what was never lost. Porphyry, his pupil and later his biographer, reports that in the six years he studied with him, Plotinus reached union with the One four times.
Plotinus did not present himself as saying anything new. He held that Plato had already laid down the fundamentals, and his classes in Rome began from readings of earlier commentaries. The treatises that came out of those classes argue, one after another, against Aristotle's followers, the Stoics, the Epicureans and the astrologers. Neoplatonism ("new Platonism"), the name for the movement that began with him, was coined by modern historians long after his death.
The sharpest challenge came from his own circle. Some of his friends were Gnostics, members of a religious movement which taught that a foolish or even malevolent maker had built the world, and he had failed to win them over. His own system placed the visible world on the lowest step of reality, yet against them he argued for its goodness and beauty.
Nor did he keep out of that world himself. Dying aristocrats left their children and their property in his care, and Porphyry's Life of Plotinus describes a house full of wards whose accounts Plotinus checked closely. With the favour of the emperor Gallienus and the empress Salonina, he asked for a ruined town in Campania to be rebuilt as a city living under Plato's Laws. Courtiers blocked the plan.
He died in 270, ill and away from Rome, on a Campanian estate left to him by his friend Zethus, with one pupil, the physician Eustochius, present. Porphyry edited the treatises three decades later as The Enneads. Through them his thought reached pagan, Jewish, Christian and early Islamic readers; Augustine came to Platonism through Latin books that carried Plotinus's teaching. Reference works today treat him as more than a commentator on Plato: an original thinker who reworked whatever he borrowed from earlier philosophers.