The late ancient philosopher Iamblichus was, alongside Plotinus and Porphyry, a founder of Neoplatonism. He established a new curriculum for the teaching of philosophy and formulated many distinctions that pervaded later Neoplatonic metaphysics. He began to mathematize all fields of philosophical concern. Most of all, he asserted that acts of transcendence, not contemplation, secure union with the divine, because it can only be reached by an equally divine faculty, which is present in every individual. Matter, soul and mind contain images of the divine and so are genuine participants in salvation.
Details of Iamblichus' life are scant. He was born at Chalcis, a descendant from an ancient line of priest-kings of Syria. In the ad 270s he studied at Caesarea (where many Christian theologians flourished). Perhaps he was still there when he heard of Porphyry, and may have visited him in Italy. They split in the ad 290s over theurgy, and Iamblichus' chief surviving work, On the Mysteries, is a record of their disagreement. He went to teach philosophy at Apamea (Syria), where the Neo-Pythagorean Numenius, and more recently Plotinus' chief follower Amelius, had flourished. The school he set up became very popular. From Pergamum his envoys converted the emperor Julian from Christianity, influencing the Athenian school of philosophy, and through it the Alexandrian school.
Iamblichus took further the programme of 'harmonization' of Greek philosophies that had been started by Porphyry: Aristotle agreed with Plato even on the Theory of Forms and on learning as recollection. He designed a curriculum for the teaching of Plato which had Aristotle as a prerequisite (see Neoplatonism §2). He also wrote grand commentaries on the two philosophers. However, he considered Pythagoras the supreme authority. Iamblichus saw number as the essence of Forms and things, and promised to make philosophy and theurgy scientific. His many treatises on Pythagoreanism mark a revival of the movement. Eight or so titles of his large number of works survive, along with reports in Proclus, Damascius and Simplicius. Later Neoplatonists were wary of Iamblichus' claims about Aristotle and Plato, but maintained his curriculum, his metaphysical distinctions and his emphasis on mathematics.
Iamblichus introduced radical revisions to Plotinus' philosophy, multiplying the ranks of being (see Plotinus §§3-4). Plotinus saw the metaphysical levels as areas of the soul's activity, with flexible and sometimes conflicting properties. Iamblichus separated psychology from ontology, and looked for distinct properties and substances in the anatomy of things. He also distinguished the 'imparticipable' from the 'participated'. Every class of things has a first principle, which retains its pure definition by being exempt from its members.
The Neoplatonic One was inferred by stripping away all attributions, but was also the first cause of being. How could the same thing transcend its products, and also be in a causal relation to them? Iamblichus promptly introduced two Ones (later Neoplatonists reverted to a single One). At the level of intellect (see Nous), he distinguished the acts of thought - the 'intellective' - from their objects - the 'intelligible'. At the level of soul (psych), he separated the individual soul from the higher: in contrast to Plotinus, for Iamblichus the individual soul descends entire into the body (see Psych). Similarly Iamblichus distinguished not only between time and timelessness, but also between a pure, eternal time and ordinary time, which is flowing.
To describe the essential nature of things, and the 'flow' or 'procession' from unity to diversity, Iamblichus turned to Neo-Pythagorean metaphysics of number. He believed that things are organized by number and relate to each other in mathematical proportion. The 'divine numbers' distribute the unity of the One to things and render them coherent. The 'intelligible numbers' stand as paradigms of the many species of reality. Intellect is organized by 'intellective numbers'. Soul exemplifies the 'mathematical numbers'. Last are the 'physical numbers', the forms immanent in matter.
Iamblichus' conclusion that the soul descends entire into matter had profound consequences. Individual souls are dominated by physical necessities (which fits with Aristotle's definition of soul as the form of biological body). But soul is still essentially divine and rational. So the embodied soul presents an uncomfortable mystery. It contains an immortal, intelligent, divine nature, but is genuinely part of a mortal, concrete, imperfect domain. The personal soul has lost touch with its deeper nature and has become self-alienated.
Iamblichus' analysis was that the transcendent cannot be grasped with mental contemplation, because the transcendent is supra-rational. Theurgy, literally 'divine-working', is a series of rituals and operations aimed at recovering the transcendent essence by retracing the divine 'signatures' through the layers of being. Education is important for comprehending the scheme of things as presented by Aristotle, Plato and Pythagoras but also by the Chaldaean Oracles (see Chaldaean Oracles). The theurgist works 'like with like': at the material level, with physical symbols and magic; at the higher level, with mental and purely spiritual practices. Starting with correspondences of the divine in matter, the theurgist eventually reaches the level where the soul's inner divinity unites with God.
See also: Neo-PythagoreanismLUCAS SIORVANES