Iamblichus was a major philosopher of the 3rd and 4th centuries CE, active in the Roman Empire. Born in Chalcis, Syria, he studied under Porphyry, a leading disciple of the Neoplatonist founder Plotinus. Iamblichus later returned to Syria to establish his own influential school, which became a center for developing later Platonic thought.

His philosophical project systematized and expanded earlier Neoplatonic ideas. A defining aspect of his work was the integration of religious ritual, known as theurgy, into philosophical practice. He argued that ritual acts were necessary for spiritual ascent, supplementing pure intellectual contemplation. According to modern scholars, this represented a decisive "Syrian" turn towards a more religious interpretation of Plato.

Iamblichus was a prolific writer, though many works survive only as fragments. His known writings include On the Pythagorean Life, a biography of Pythagoras; the Protrepticus, an exhortation to philosophy; and several treatises on the metaphysical significance of mathematics. His most famous work, On the Mysteries of the Egyptians, is a major defense of ritual theurgy, though some modern scholars debate its attribution to him. He also wrote extensive, now fragmentary, commentaries on Plato’s dialogues.

Iamblichus is a pivotal figure for making theurgy a central component of later Neoplatonism. His complex hierarchy of divine levels and his justification of ritual practice directly influenced the major Athenian Neoplatonic schools of the 5th and 6th centuries, shaping thinkers like Proclus and, indirectly, later medieval and Renaissance thought.