Neoplatonists thought they were simply reading Plato correctly
For more than a thousand years, readers took it for granted that Plotinus and his successors had explained what Plato truly meant. Only around the early nineteenth century did scholars separate Plato from these third-century interpreters and give them a new name, Neoplatonism, a label some experts still find misleading.
The movement is usually traced to Ammonius Saccas and his pupil Plotinus, who lived from about 205 to 270 AD, and it ran into the sixth century. Its core idea is that all reality flows from a single source, the One. Plotinus described this One as utterly without division, beyond being and non-being alike, prior to anything that exists. From it emanates Intellect, or nous, which in turn produces the world-soul. His Enneads, edited by his student Porphyry, mix theory about the soul's lofty origin with practical guidance for its return.
Successors took the system in different directions. Porphyry wrote on astrology, music and Euclid, and composed fifteen books against the Christians, of which only fragments remain. Iamblichus filled the gap between the One and matter with crowds of divine beings open to prayer, and taught that the soul climbs back through ritual, called theurgy. Later, Proclus inserted a layer of henads, identified with the Greek gods, between the One and Intellect. In Alexandria the philosopher Hypatia headed the Platonist school until she was killed by a mob in 415.
Even the founder's teacher was contested. Christian writers such as Eusebius and Jerome insisted Ammonius stayed Christian, while Porphyry said he abandoned the faith for philosophy. Resemblances to Samkhya thought have led several authors to propose Indian influence through him.
The ideas travelled remarkably far. Arabic and Persian translations shaped al-Farabi and Avicenna; Solomon ibn Gabirol and Maimonides drew on them too. Thomas Aquinas read Proclus directly, Meister Eckhart pointed to a Godhead beyond the nameable God, and in the Italian Renaissance Marsilio Ficino championed the tradition as an authentic account of Plato. The modern split came slowly; Friedrich Schleiermacher is often cited as an early figure who treated Plato's philosophy separately from these later readers.
Source: Neoplatonism
