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".