Plato's five-fold classifications in relation to the metaphysics of the middle-Platonists

Abstract

The Parmenides shows Plato's concern to relate the various branches of reality which he had earlier discerned; modifying the ontology of Republic VI, he sought to combine four worlds into one in the third of five positive hypotheses. The Sophist then attempts to show that reality is five; the five components are echoed in the "Psychogony" of the Timaeus, in which work Plato is confronted with a choice between one world and five. Two cryptic classifications from the Philebus suggest Plato’s continued interest in the number, and the Epinomis and Seventh Letter show that the Academy knew of this. Speusippus, depending heavily on the Parmenides, adopted a system of five separate "existences", each with their own first-principles. Xenocrates, though favouring tripartitions, preserved a framework in which the five-fold concept of the whole became understandable. Academic scepticism made it necessary for Posidonlus and Antiochus to look back to the works of Xenocrates for guidance, from whom they received an Old-Academic understanding of the Master and new interest in Speusippus. Through this latter Pythagoreans learned to interpret the Parmenides; through him also Theodorus learned to misinterpret the Timacus, The Philebus grew in importance, the final classification being authoritative for Arius, Plutarch, and Albinus. Seneca attributes five causes to Plato, Plutarch regards the number as of supreme philosophical importance, Albinus' writings echo this view. Theon, Maximus, and Numenius conform in different ways with a tradition that respects a five-fold metaphysic.