He wrote original works in the Greek language on a wide variety of topics, ranging from music theory to Homer to vegetarianism.

[4] In 262 he went to Rome, attracted by the reputation of Plotinus, and for six years devoted himself to the practice of Neoplatonism, during which time he severely modified his diet, at one point becoming suicidal.

On returning to Rome, he lectured on philosophy and completed an edition of the writings of Plotinus (who had died in the meantime) together with a biography of his teacher.

Apart from writing the Aids to the Study of the Intelligibles (Ἀφορμαὶ πρὸς τὰ νοητά; Sententiae ad Intelligibilia Ducentes), a basic summary of Neoplatonism, he is especially appreciated for his Introduction to Categories (Introductio in Praedicamenta or Isagoge et in Aristotelis Categorias Commentarium), a very short work often considered to be a commentary on Aristotle's Categories, hence the title.

The Introduction describes how qualities attributed to things may be classified, famously breaking down the philosophical concept of substance into the five components genus, species, difference, property, and accident.

With the Arabicized name Isāghūjī (إيساغوجي) it long remained the standard introductory logic text in the Muslim world and influenced the study of theology, philosophy, grammar, and jurisprudence.

Porphyry is also known as an opponent of Christianity and defender of Paganism; his precise contribution to the philosophical approach to traditional religion may be discovered in the fragments of Philosophy from Oracles (Περὶ τῆς ἐκ λογίων φιλοσοφίας; De Philosophia ex Oraculis Haurienda), which was originally three books in length.

[e] Whether or not Porphyry was the pagan philosopher's opponent in Lactantius' Divine Institutes, written at the time of the persecutions, has long been discussed.

The fragments contain oracles identifying proper sacrificial procedure, the nature of astrological fate, and other topics relevant to Greek and Roman religion in the third century.

Whether this work contradicts his treatise defending vegetarianism, which also warned the philosopher to avoid animal sacrifice, is disputed among scholars.

[15] During his retirement in Sicily, Porphyry wrote Against the Christians (Κατὰ Χριστιανῶν; Adversus Christianos) which consisted of fifteen books.

In fact, everything known about Porphyry's arguments is found in these refutations, largely because Theodosius II ordered every copy burned in AD 435 and again in 448.