|A bust of Plotinus|
Plotinus decided to become a philosopher in his 28th year—what he used to do before that is not known. His quest for philosophical knowledge brought him to Alexandria where he studied under a teacher called Ammonius Saccas for eleven years. Little is known about Ammonius own philosophical views, but he encouraged Plotinus to study Plato. In 243, Plotinus, aspiring to study Persian and Indian philosophy, attached himself to the expedition of Emperor Gordian III to Persia. But when the expedition got aborted, with the assassination of Gordian by his troops, Plotinus abandoned his plans and established himself in Rome in 245, where he lived till his death in 270 or 271.
According to Porphyry, for ten years Plotinus didn’t write anything himself—he devoted himself to lecturing on the philosophy that he had learned from his master Ammonius. After that he began setting down his thoughts in a series of "treatises" of various lengths and complexity. Porphyry arranged Plotinus’s treatises into six groups of nine each—which got the title Enneads, because in Greek “enneads” means nine. Porphyry offers an astonishing information about Plotinus—he notes that due to his poor eyesight, Plotinus never revised anything he wrote.
Plotinus thought of himself as a disciple of Plato. Today he is regarded as the founder of "Neoplatonism," but he would have preferred the label "Platonism" for his work. His philosophy was devoted to responding to Plato's critics (this includes Aristotle, the Stoics, Epicureans, Skeptics, and various lesser figures) and elucidating the wisdom of Plato.