"Neo-platonism (or Neoplatonism) is a modern term used to designate the period of Platonic philosophy beginning with the work of Plotinus and ending with the closing of the Platonic Academy by the Emperor Justinian in 529 C.E. This brand of Platonism, which is often described as ‘mystical’ or religious in nature, developed outside the mainstream of Academic Platonism. The origins of Neoplatonism can be traced back to the era of Hellenistic syncretism which spawned such movements and schools of thought as Gnosticism and the Hermetic tradition. A major factor in this syncretism, and one which had an immense influence on the development of Platonic thought, was the introduction of the Jewish Scriptures into Greek intellectual circles via the translation known as the Septuagint. The encounter between the creation narrative of Genesis and the cosmology of Plato’s Timaeus set in motion a long tradition of cosmological theorizing that finally culminated in the grand schema of Plotinus’ Enneads. Plotinus’ two major successors, Porphyry and Iamblichus, each developed, in their own way, certain isolated aspects of Plotinus’ thought, but neither of them developed a rigorous philosophy to match that of their master. It was Proclus who, shortly before the closing of the Academy, bequeathed a systematic Platonic philosophy upon the world that in certain ways approached the sophistication of Plotinus. Finally, in the work of the so-called Pseudo-Dionysius, we find a grand synthesis of Platonic philosophy and Christian theology that was to exercise an immense influence on mediaeval mysticism and Renaissance Humanism."
"Plotinus is considered to be the founder of Neoplatonism. Taking his lead from his reading of Plato, Plotinus developed a complex spiritual cosmology involving three foundational elements: the One, the Intelligence, and the Soul. It is from the productive unity of these three Beings that all existence emanates, according to Plotinus. The principal of emanation is not simply causal, but also contemplative. In his system, Plotinus raises intellectual contemplation to the status of a productive principle; and it is by virtue of contemplation that all existents are said to be united as a single, all-pervasive reality. In this sense, Plotinus is not a strict pantheist, yet his system does not permit the notion of creatio ex nihilo (creation out of nothingness). In addition to his cosmology, Plotinus also developed a unique theory of sense-perception and knowledge, based on the idea that the mind plays an active role in shaping or ordering the objects of its perception, rather than passively receiving the data of sense experience (in this sense, Plotinus may be said to have anticipated the phenomenological theories of Husserl). Plotinus’ doctrine that the soul is composed of a higher and a lower part — the higher part being unchangeable and divine (and aloof from the lower part, yet providing the lower part with life), while the lower part is the seat of the personality (and hence the passions and vices) — led him to neglect an ethics of the individual human being in favor of a mystical or soteric doctrine of the soul’s ascent to union with its higher part. The philosophy of Plotinus is represented in the complete collection of his treatises, collected and edited by his student Porphyry into six books of nine treatises each. For this reason they have come down to us under the title of the Enneads."
"Porphyry (234?–305? C.E.) was a Neoplatonist philosopher born in Tyre in Phoenicia. He studied with Longinus in Athens and then with Plotinus in Rome from 263–269 C.E. and became a follower of the latter's version of Platonism. Porphyry wrote in just about every branch of learning practiced at the time but only a portion of his large output is extant. Porphyry was an influential thinker. He applied Neoplatonism to pagan religion and other spheres and is, as such, a key figure in the promulgation of Neoplatonic thought. His writings on Aristotle's logical works, preserved in part and influential in the Latin West through Boethius' translations, contain attempts to harmonize Aristotle's logical writings with Platonism."
"Proclus of Athens (*412–485 C.E.) was the most authoritative philosopher of late antiquity and played a crucial role in the transmission of Platonic philosophy from antiquity to the Middle Ages. For almost fifty years, he was head or ‘successor’ (diadochos, sc. of Plato) of the Platonic ‘Academy’ in Athens. Being an exceptionally productive writer, he composed commentaries on Aristotle, Euclid and Plato, systematic treatises in all disciplines of philosophy as it was at that time (metaphysics and theology, physics, astronomy, mathematics, ethics) and exegetical works on traditions of religious wisdom (Orphism and Chaldaean Oracles). Proclus had a lasting influence on the development of the late Neoplatonic schools not only in Athens, but also in Alexandria, where his student Ammonius became the head of the school. In a culture dominated by Christianity, the Neoplatonic philosophers had to defend the superiority of the Hellenic traditions of wisdom. Continuing a movement that was inaugurated by Iamblichus (4th c.) and the charismatic figure of emperor Julian, and following the teaching of Syrianus, Proclus was eager to demonstrate the harmony of the ancient religious revelations (the mythologies of Homer and Hesiod, the Orphic theogonies and the Chaldaean Oracles) and to integrate them in the philosophical tradition of Pythagoras and Plato. Towards this end, his Platonic Theology offers a magisterial summa of pagan Hellenic theology. Probably the best starting point for the study of Proclus’ philosophy is the Elements of Theology (with the masterly commentary by E.R. Dodds) which provide a systematic introduction into the Neoplatonic metaphysical system."