[...] Proclus, a sharp and knowledgeable mind, without strict scientific argumentation, will combine in a detailed and complete, but particularly complex and difficult to understand system, the entire Neoplatonic philosophy as it had been formed up to his time. With artistic skill, he will shape a unified system that will include the supreme god (the One or the Good), the individual gods, the angels, the demons, the souls, and other higher and lower beings. We cannot attribute pioneering ideas to Neoplatonism (perhaps this was not possible after such a long and diverse history of this philosophical school), but we must certainly attribute to it a complete systematization of Neoplatonic cosmology, as well as its transmission, as a unified system, to the Christian scholastic Middle Ages.
[...] (from the introduction of the book)