Statements and fragments of his apparently very numerous works have been preserved by Origen, Theodoret, and especially by Eusebius, and from them we may learn the nature of his Platonist-Pythagorean philosophy, and its approximation to the doctrines of Plato.
Numenius was a Neopythagorean, but his object was to trace the doctrines of Plato up to Pythagoras, and at the same time to show that they were not at variance with the dogmas and mysteries of the Brahmins, Jews, Magi and Egyptians.
[3] His intention was to restore the philosophy of Plato, the genuine Pythagorean and mediator between Socrates and Pythagoras in its original purity, cleared from the Aristotelian and Stoic doctrines, and purified from the unsatisfactory and perverse explanations, which he said were found even in Speusippus and Xenocrates, and which, through the influence of Arcesilaus and Carneades had led to a bottomless skepticism.
[4] His work on the apostasy of the Academy from Plato, to judge from its rather numerous fragments,[5] contained a minute and wearisome account of the outward circumstances of those men, and was full of fabulous tales about their lives, without entering into the nature of their skepticism.
George Karamanolis from the Stanford Encyclopedia of Philosophy noted, "The remains of Numenius' work leave no doubt that he relied primarily on texts of Plato in constructing his own system of principles.
"[6] His books On the Good (Peri Tagathou – Περὶ Τἀγαθοῦ) seem to have been of a better kind; in them he had minutely explained, mainly in opposition to the Stoics, that existence could neither be found in the elements because they were in a perpetual state of change and transition, nor in matter because it is vague, inconstant, lifeless, and in itself not an object of our knowledge; and that, on the contrary, existence, in order to resist the annihilation and decay of matter, must itself rather be incorporeal and removed from all mutability,[7] in eternal presence, without being subject to the variation of time, simple and imperturbable in its nature by its own will as well as by influence from without.
Numenius wanted to show that the Jewish nation must be counted among the ancient ones that have a share in logos and also that Moses had a conception of the first principle similar to that of Plato, since both identified God with being.
Leemans, Studie over den Wijsgeer Numenius van Apamea met Uitgave der Fragmenten, Brussels 1937; E. Des Places, Numénius, Fragments, Collection Budé, Paris: Les Belles Lettres, 1973; and Robert Petty, The Fragments of Numenius of Apamea: Text, Translation and Commentary (2012) Westbury, UK.