Porphyry (Porphyrios) (AD 233–c.305), Neoplatonist philosopher originally from Tyre. He is known by the Greek version of his original Phoenician name Malchus, ‘king’. He studied philosophy at Athens and was converted to Neoplatonism by Plotinus whom he met at Rome in 262. He was particularly hostile to Christianity. His work Against the Christians was burnt in the fifth century, and is now known only through quotations. He was the author of numerous philosophical works including a history of philosophy down to Plato, from which a life of Pythagoras survives. His most important work was the editing of the lectures of Plotinus under the title Enneads, and the composition of Plotinus' biography. His ‘Introduction’ (Īsagōgē) to the ‘Categories’ of Aristotle was later translated into Latin by Boethius and became very influential in the medieval schools.

(c. AD 232-305) Syrian polymath, and disciple and editor of Plotinus. Porphyry also wrote commentaries upon Plato and Aristotle. His most influential work was the Isagoge or Introduction to Aristotle's Categories, which was responsible for the classic formulation of the problem of universals, as it preoccupied Boethius and subsequent medieval philosophy. At the beginning of the Isagoge Porphyry asks: ‘Do genera and species subsist in themselves, or do they exist only in the mind? If they subsist in themselves, are they corporeal or incorporeal? If they are incorporeal, do they exist in separation from sensible substances or in conjunction with them?’ The tree of Porphyry is the method of classification by dichotomy: per genus et differentiam. Porphyry's distinction is as a transmitter of other peoples' work. Even his major editor and commentator, J. Bidez, in his Vie de Porphyre (1913), confesses that in the entire extant work of Porphyry there ‘is not a thought or an image which one can confidently affirm to be his own’.

(pôr'fĭrē) , c.232–c.304, Greek scholar and Neoplatonic philosopher. He studied rhetoric under Cassius Longinus and philosophy under Plotinus. He later lectured in Rome on the philosophy of Plotinus and was the teacher of the Neoplatonist Iamblichus. He wrote lives of Pythagoras and of Plotinus and edited the Enneads of Plotinus. He wrote extensively against Christianity and on rhetorical and literary themes. His most influential work is the Isagoge, an introduction to the logic of Aristotle, which became a standard medieval text.