Six Nines

Plotinus never gave his own writings a title or arranged them into a single work; what survives as the Enneads is entirely the doing of his student Porphyry, who collected fifty-four individual treatises Plotinus had written over roughly two decades of teaching in Rome and, working from Plotinus's own instruction that Porphyry edit and arrange the material after his death, organized them by subject into six groups of nine treatises each, a number chosen deliberately for its numerological completeness rather than because the treatises fell naturally into that shape.

Ennea is simply the Greek word for nine, and the title Enneads, six sets of nine, describes Porphyry's editorial arrangement rather than anything Plotinus himself called his work. Porphyry grouped the material roughly by theme, moving from ethical and psychological questions in the earlier Enneads toward cosmology, the nature of Intellect, and finally the highest and most difficult subject, the One itself, in the sixth, an order meant to lead a reader upward through increasingly abstract levels of reality in imitation of the soul's own philosophical ascent. Porphyry also wrote a Life of Plotinus as an introduction to the completed edition, which remains the single most detailed biographical source for Plotinus and for the working practices of his Roman philosophical circle.