  Numenius, a Platonist philosopher of the mid 2nd century CE, had considerable impact on later Platonism, most notably on Plotinus (3rd c.) and Porphyry (3rd-4th c.  His work survives only in fragments, either as excerpts or in reports in later sources, mostly Platonists, both pagan and Christian (e.g. Porphyry, Proclus, Calcidius, Origen, Eusebius). Numenius' work is important both historically and philosophically. Its historical significance lies mainly in that it shows how much of Plotinus' philosophy, especially Plotinus' metaphysics, was inspired by earlier Platonists such as Numenius, who was one of the authors read in Plotinus' seminar (Porphyry, Life of Plotinus 14.12).  Plotinus' debt to Numenius' philosophy was much debated already by Platonists of Plotinus' generation (ibid. 18.2–3, 17.1–23). This discussion shows that Plotinus was not considered in his own time to have initiated a new and distinct movement in Platonism—what we today call Neoplatonism. He was rather seen as simply continuing and developing the philosophy of previous Platonists, Numenius being prominent among them, just as they themselves had developed in similar fashion the work of their own Platonist predecessors. Numenius' significance also lies in his impact on the thought of early Christian thinkers like Origen and Eusebius, who are captured by Numenius' references to Hebrews and see in his theology a prefiguration of their trinitarian doctrine. Philosophically, Numenius' work is important because he, like Eudorus and Moderatus (1st c. CE), tried to construct a hierarchical system of intelligible principles (archai) of reality, but unlike them he held that intelligible principles are responsible only for the order of the world, wherein its goodness lies, while matter has an existence independent of these principles and accounts for disorder and badness. In this sense Numenius maintains a dualism in metaphysics that has affinities with that of Plutarch. Numenius' system of three principles of reality, similar to Plotinus' hypostases of One, Intellect and Soul, was constructed on the basis of accounts of the intelligible world and its primacy, and of the soul as a spiritual substance essentially related to that world, in Plato. More specifically, it results from reflection on the Form of the Good in Republic VI, the demiurge and the world-soul of the Timaeus, and the One of the Parmenides. The hierarchical order of these principles of reality is determined by the degree of unity and simplicity of each; the highest principle is the simplest and most completely a unity. It is also absolutely good and transmits goodness.