Iamblichus' Cosmology
At the head of his system, Iamblichus placed the transcendent incommunicable "One", the monad, whose first principle is intellect, nous. Immediately after the absolute One, lamblichus introduced a second superexistent "One" to stand between it and 'the many' as the producer of intellect, or soul, psyche. This is the initial dyad. The first and highest One (nous), which Plotinus represented under the three stages of (objective) being, (subjective) life, and (realized) intellect, is distinguished by Iamblichus into spheres of intelligible and intellective, the latter sphere being the domain of thought, the former of the objects of thought. These three entities, the psyche, and the nous split into the intelligible and the intellective, form a triad.
Between the two worlds, at once separating and uniting them, some scholars think there was inserted by lamblichus, as was afterwards by Proclus, a third sphere partaking of the nature of both. But this supposition depends on a merely conjectural emendation of the text. We read, however, that in the intellectual triad he assigned the third rank to the Demiurge. The Demiurge, the Platonic creator-god, is thus identified with the perfected nous, the intellectual triad being increased to a hebdomad. The identification of nous with the Demiurge is a significant moment in the Neoplatonic tradition and its adoption into and development within the Christian tradition. St. Augustine follows Plotinus by identifying nous, which bears the logos, with the creative principle. Whereas the Hellenes call that principle the Demiurge, Augustine identifies the activity and content of that principle as belonging to one of the three aspects of the Divine Trinity -- the Son, who is the Word (logos). Iamblichus and Plotinus commonly assert that nous produced nature by mediation of the intellect, so here the intelligible gods are followed by a triad of psychic gods.
The first of these "psychic gods" is incommunicable and supramundane, while the other two seem to be mundane, though rational. In the third class, or mundane gods, there is a still greater wealth of divinities, of various local position, function, and rank. Iamblichus wrote of gods, angels, demons and heroes, of twelve heavenly gods whose number is increased to thirty-six or three hundred and sixty, and of seventy-two other gods proceeding from them, of twenty-one chiefs and forty-two nature-gods, besides guardian divinities, of particular individuals and nations. The realm of divinities stretched from the original One down to material nature itself, where soul in fact descended into matter and became "embodied" as human beings. Basically, Iamblichus greatly multiplied the ranks of being and divine entities in the universe, the number at each level relating to various mathematical proportions. The world is thus peopled by a crowd of superhuman beings influencing natural events and possessing and communicating knowledge of the future, and who are all accessible to prayers and offerings.
The whole of Iamblichus's complex theory is ruled by a mathematical formalism of triad, hebdomad, etc., while the first principle is identified with the monad, dyad and triad; symbolic meanings being also assigned to the other numbers. The theorems of mathematics, he says, apply absolutely to all things, from things divine to original matter. But though he subjects all things to number, he holds elsewhere that numbers are independent existences, and occupy a middle place between the limited and unlimited.
Another difficulty of the system is the account given of nature. It is said to be bound by the indissoluble chains of necessity called fate, and is distinguished from divine things that are not subject to fate. Yet, being itself the result of higher powers becoming corporeal, a continual stream of elevating influence flows from them to it, interfering with its necessary laws and turning to good ends the imperfect and evil. Of evil no satisfactory account is given; it is said to have been generated accidentally in the conflict between the finite and the infinite.
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