Movement initiated by Plotinus (AD 205-70) and carried forward by various philosophers of the next three centuries, having repercussions in the Renaissance especially among the Cambridge Platonists of the 17th century and, later, Georg Wilhelm Friedrich Hegel (1770-1831).
Neo-Platonism claimed to interpret Plato (c.427-c.347 BC), and to reconcile Aristotle (384-322 BC) with Plato, though modern scholars dispute its success in either claim. It borrowed from other schools, but opposed epicureanism.
Reality is seen as hierarchically ordered, having at its apex a spiritual entity or ‘hypo-stasis’, usually called the One, which is unknowable and ineffable and can be described only indirectly (negatively by abstraction, or by analogy).
Other hypostases are derived from this by a process called ’emanation’ (hence emanationism as a name for neo-Platonism): first intellect (nous), then soul (psyche, including discursive reason), and finally matter.
These stages involve manifestations of the One, but of decreasing perfection and actuality; the changing world around us, for instance, involves potentialities that are not always actualized, and evil can only arise as a privation and where there is change and unrealized potentiality.
A H Armstrong, ed., Cambridge History of Later Greek and Early Medieval Philosophy, 2nd edn (1970)