A later form of Platonic philosophy that had its primary development as a school of thought in the Roman Empire from the third to the fifth century AD. Countering dualistic interpretations of Plato's thought, it is a highly monistic version, namely, one that posits a superexistent Source of all being that extends itself into various lower levels of being, with each lower level being a weaker extended expression of the level just above it. Its founder was Plotinus (204-70), a Hellenized Egyptian who at the age of 40 established an academy of philosophy in Rome and taught in it for the next twenty-five years. Some of its basic tenets, however, likely came from his teacher, Ammonius Saccas (185-250), with whom he had studied philosophy in Alexandria for eleven years when he was a young man. The term 'Neoplatonism' itself is of fairly recent origin, going back only to the mid-nineteenth century when German scholars first used it to distinguish the views of the later Greek and Roman Platonists from those of Plato.