Neoplatonism is a version of Platonic philosophy that emerged in the 3rd century AD against the background of Hellenistic philosophy and religion. The term does not encapsulate a set of distinct ideas based on a form of Platonism as much as a series of Platonic thinkers coming primarily from a certain ancient historical period. Among the common ideas it maintains is monism, the doctrine that all of reality can be derived from a single principle, "the One".
Neoplatonism began with Ammonius Saccas and his student Plotinus (c. AD 205 – 271) and stretched to the sixth century. After Plotinus there were three distinct periods in the history of Neoplatonism: the work of his student Porphyry (third to early fourth century); that of Iamblichus (third to fourth century); and the period in the fifth and sixth centuries, when the academies in Alexandria and Athens flourished.