Plotinus
Plotinus is considered to be the founder of Neo-Platonism. Taking his lead from his reading of Plato, Plotinus developed a complex spiritual cosmology involving three hypostases: the One, the Intelligence, and the Soul. It is from the productive unity of these three Beings that all existence emanates.
(Cheers to dtj!)
Link coming up as I'm not allowed to post it... 😠