Enneads

The collected treatises of Plotinus, arranged after his death by his student Porphyry into six groups of nine, hence the name, and prefaced with Porphyry's Life of Plotinus. The order runs roughly from ethics through physics and soul to intellect and the One. Plotinus presents himself as an interpreter of Plato, but the system is his own. All reality derives from the One, which is beyond being and thought and produces without being diminished, as light radiates from the sun. From it comes Intellect, which thinks the Forms, and from Intellect comes Soul, which animates the cosmos and individual bodies. Matter, at the furthest remove, is privation and the source of evil. The human task is to turn inward and rise, through virtue and contemplation, back toward the One. Treatises such as On Beauty (I.6) shaped Christian, Islamic and Renaissance thought about beauty and the ascent of the soul.

It is the source of Neoplatonism, the philosophy that carried Plato into Christian, Islamic and Jewish thought for more than a thousand years.