Neoplatonism (less precisely Late (Antique) Platonism) is a modern term for an ancient sub-tradition of Platonic philosophy, initiated by Plotinus of Lycopolis when he began to teach in Rome in the mid-3rd century CE. The last pagan philosophers who can still be called Neoplatonists without reservation were teaching in the latter half of the 6th century, but the reception of Neoplatonism is also extremely important to the subsequent history of (mostly non-pagan) philosophy, down to the modern day. The extent of this influence is often understated or ignored by historians – but also vastly exaggerated by a few.

Since Plotinus’ ideas emerged from close engagement with his Platonic predecessors and contemporaries and their varied ideas, and his later followers felt free to introduce innovations into their teaching, there are very few or no doctrines which are both unique to the Neoplatonists and shared by all of them. What makes them a recognizable sub-school, instead, is that they not only sought to interpret Plato, but also to progressively build on their predecessors, whom they represented as a continuous lineage from Plotinus on.

One striking feature of the development of the school after the death of Plotinus is the adoption of additional authorities to complement or support Plato. These included Plato’s student Aristotle – the survival of whose works is owed to the Neoplatonists –; inspired poets including Homer, Hesiod, and especially Orpheus; and the works of the Chaldaeans, especially the so-called Chaldaic Oracles which were held to be revelations from the gods. The Orphic and Chaldaic works in question are now unfortunately lost, but the Neoplatonists preserve much from them.