Iamblichus (c.245-c.325 A.D.) is the single most important representative of Neoplatonism after Plotinus and the prime defender of the ritual and symbolic methods of union with the divine that are generally known as theurgy. His influence for the development of Platonic philosophy up to (and including) the Renaissance was very decisive.
Iamblichus was born in Chalkis of northern Syria into a noble family. Amelius and Porphyry are reported to have been his teachers. After the conclusion of his studies Iamblichus settled down in Apameia of Syria, where he established his own school.
Iamblichus wrote a voluminous commentary in the Chaldaean Oracles, commentaries on several Platonic dialogues and Aristotelian treatises as well as some systematic works. All those texts have been lost. Of surviving works the most important are the following: On the Egyptian Mysteries, On Pythagorean life, Exhortation to Philosophy.
The On the Egyptian Mysteries – the title is much later than the work, and very misleading at that – is the sole treatise devoted to the philosophy of religion surviving from Graeco-Roman antiquity; most probably it was also the first. Its aim is to show that the desirable salvation of the human soul cannot be achieved through theoretical contemplation and knowledge, as in Plotinus, but necessarily requires the assistance of divine grace, which is provided through active participation in sacred ceremonies and rituals.
Iamblichus was the first to have accepted the divine provenance of the Chaldaen Oracles and the efficiency of theurgy. He believed that during the performance of sacred acts the gods freely attune to what is done in the material sphere and decide, out of their own unrestricted will, to provide aid to intrinsic human deficiency.
Although Iamblichus generally followed the tripartite structure of metaphysical principles established by Plotinus, he still introduced some novel distinctions which determined the prevalent modes of thought of all later Neoplatonists. It is not by accident that Iamblichus is the only thinker, besides Plato himself, who is called “divine” in the texts of his successors. Today he is regarded as the second founder of Neoplatonism.