Neo-Platonism has its roots in Platonism, the philosophy outlined by the Greek philosopher Plato (died 347 B.C.). One of the distinguishing features of Platonism is its assertion that the visible, tangible forms of the physical world are based on immaterial models, called Forms or Ideas. Tangible forms are transitory, unstable, and imperfect, whereas ideal Forms are eternal, perfect, and unchanging. Physical forms are many and diverse, but ideal Forms are single and unified. Platonism places a definite hierarchy of value on these qualities: Eternity is superior to the temporal; unity is superior to division; the immaterial is superior to the material. In Platonism, the fleeting physical world that humankind inhabits becomes a kind of flawed manifestation of a perfect and eternal model that can be perceived only by the intellect, not by the senses.
The Neo-Platonist philosophers Plotinus (c. 205–270 A.D.) and his disciple Porphyry (232–c.300 A.D.) expanded Plato's philosophical ideas into something more like a full-fledged cosmology. In the Enneads, Plotinus proposed a supreme divinity with three aspects. The "One" is a transcendent, ineffable, divine power, the source of everything that exists. It is complete and self-sufficient. Its perfect power overflows spontaneously into a second aspect, the Intelligence (Mind or Nous), which contemplates the power of the One. By contemplating the One, the Intelligence produces Ideas or Forms. The unity of the One thus overflows into division and multiplicity. These Forms are translated into the physical world through the creative activity of the World Soul. In the immaterial realm, the higher part of the Soul contemplates the Intelligence, while in the material realm, the lower part of the Soul acts to create and govern physical forms. According to Plotinus, the Soul, in descending from the immaterial to the material world, forgets some of its divine nature. All human individual souls, therefore, share in the divinity of the One and will eventually return to the divine realm from which they came, after they shed their physical bodies. Porphyry further developed Plotinus' ideas about the soul, asserting that individual human souls are actually separate from and lower than the World Soul. However, by the exercise of virtue and contemplation of the spiritual, the human soul can ascend from the lower, material realm, toward the highest good, the absolute beauty and perfection of the immaterial One. Augustine refers to this Platonic "ascent of the soul" in Book 9 of the Confessions.
Christians, for their part, were deeply suspicious of Platonism and of all the old pagan philosophies that Christianity had superseded. Nonetheless, Neo-Platonism had qualities that made it attractive to intellectual Christians. Neo-Platonism's three-fold model of divinity fit well with the Christian doctrine of the Holy Trinity. Neo-Platonism's stress on the transcendent, immaterial realm as the highest good also appealed to the ascetic streak in Christianity. Augustine found Neo-Platonism to contain all the major ideas of Christianity, with the important exception that it did not acknowledge Christ.
