He returned to Coele Syria around 304 to found a school in Apamea (near Antioch), a city known for its neoplatonic philosophers.

Iamblichus designed a curriculum for studying Plato and Aristotle, and wrote commentaries on the two which survive only in fragments.

Pythagoras was his supreme authority, and he wrote the ten-volume Collection of Pythagorean Doctrines with extracts from several ancient philosophers; only the first four volumes and fragments of the fifth survive.

Plotinus represented the Nous as three stages: objective being, subjective life, and realized intellect.

Augustine of Hippo follows Plotinus, identifying the nous with logos (the creative principle) as part of the Trinity.

His divine realm extends from the Monad to material nature, where the soul descends into matter and becomes embodied in human form.

These superhuman beings influence natural events and communicate knowledge about the future, and are accessible with prayers and offerings.

The Roman emperor Julian, not content with Eunapius' modest eulogy that Iamblichus was inferior to Porphyry only in style, regarded him as second only to Plato and said that he would give all the gold in Lydia for one of his letters.