Under him Avicenna read the Isagoge of Porphyry and the first propositions of Euclid.
Joachim Jung, in his Isagoge phytoscopica (1678), recognized that the plant-body consists of certain definite members, root, stem and leaf, and defined them by their different form and by their mutual relations.
He translated into Latin Aristotle's Analytica Priora et Posteriora, the Topica, and Elenchi Sophistici; and he wrote commentaries on Aristotle's Categories, on his book lrEpi Epµnvcias, also a commentary on the Isagoge of Porphyrius.
A single sentence in Porphyry's Isagoge or " introduc tion " to the Categories of Aristotle furnished the i o, s text of the discussion.
Porphyry, the Neoplatonist, the disciple of Plotinus, was an unknown personage to those early students of the Isagoge.