Plotinus was a major Greek-speaking philosopher of the ancient world. In his philosophy, described in the Enneads, there are three principles: the One, the Intellect, and the Soul.
Historians of the 19th century invented the term Neoplatonism and applied it to him and his philosophy which was influential in Late Antiquity. Neoplatonism is a term used to designate a strand of Platonic philosophy that emerged in the third century AD against the background of Hellenistic philosophy and religion. The term does not encapsulate a set of ideas as much as it encapsulates a chain of thinkers which began with Ammonious Saccas and his student Plotinus (c. 204/5 – 270 AD) and which stretches to the sixth century AD. Even though Neoplatonism primarily circumscribes the thinkers who are now labeled Neoplatonists and not their ideas, there are some ideas that are common to Neoplatonic systems, for example, the monistic idea that all of reality can be derived from a single principle, "the One".
Plotinus metaphysical writings have inspired centuries of Pagan, Islamic, Jewish, Christian, and Gnostic metaphysicians and mystics.