Porphyry was a neoplatonist, a student of the leading neoplatonist Plotinus. Porphyry's criticism of the Aristotelian Categories raised the profound question of their existential status. The categories are the most general "predicables," the things (the "concepts?") that can be said or predicated of "objects." In some sense, this is the beginning of analytic language philosophy. Later thinkers divided over whether the categories are real things (the "Realists") or just words or names (the "Nominalists"). Like Plato and all the neoPlatonists, Porphyry disliked the idea of material things (including the body), regarding them as subordinate to the Platonic ideas" (ιδεα), and merely poor copies (mimesis) of those ideas. For Porphyry, the Platonic realm of ideas is the source of eternal "being," whereas the material world is ephemeral and mere "becoming." And the ultimate "Being" for Porphyry is the idea of "The One," which included the Platonic ideals of the True, the Good, and the Beautiful. Where these ideas are perfectly singular, all lesser ideas contain internal differences, describable (or predicable) as properties or attributes of their substance. Thus Socrates (a substance) is a Man (a property). Aristotle's five categories (see Topics, a iv. 101 b 17-25) are definition (horos) [Porphyry substituted Plato's idea (eidos), later writers use species], genus (genos), difference (diaphora), property (idion), and accident (symbebekos). In his Introduction to the Aristotelian Categories (the Isagoge), Porphyry raised what became known as his "fateful question." Can these categories be said to exist (in the sense of material existence)? As a neoPlatonist, Porphyry might have been quite satisfied to have the categories simply exist in the "metaphysical" realm of the ideas? He clearly sees that they are concepts. Information philosophy identifies them as immaterial physical things, with causal power.Normal | Teacher | Scholar
Since it is necessary, Chrysaorius, both to the doctrine of Aristotle's Categories, to know what genus, difference, species, property, and accident are, and also to the assignments of definitions, in short, since the investigation of these is useful for those things which belong to division and demonstration, I will endeavour by a summary briefly to discuss to you, as in the form of introduction, what on this subject has been delivered by the ancients, abstaining, indeed, from more profound questions, yet directing attention in a fitting manner, to such as are more simple. For the moment, I shall naturally decline to say, concerning genera and species, whether they subsist (in the nature of things), whether they are bare, pure isolated conceptions, whether, if subsistent, they are corporeal or incorporeal, or whether they are separated from or in sensible objects, and other related matters. This sort of problem is of the very deepest, and requires more extensive investigation.A major goal of information philosophy is to establish the existential status of the "metaphysical" ideal world and to show how interactions with the material world are not only possible, but essential to the creation of new information, new ideas, in an open future.