Isagoge (Mediaeval Sources in Translation)

Porphyry of Tyre, (A. D. 234-c. 305) was a Neo-Platonic philosopher, born in Tyre. Porphyry's parents were Phoenician, and he was born Malchus ("king") in Tyre. His teacher in Athens, Cassius Longinus, gave him the name Porphyrius ("clad in purple"), a punning allusion to the color of the imperial robes. Under Longinus he studied grammar and rhetoric. In 262 he went to Rome, attracted by the reputation of Plotinus, and for six years devoted himself to the study of Neo-Platonism.

He edited and published the Enneads, the only collection of the work of his teacher Plotinus. He also wrote many works himself on a wide variety of topics. His Isagoge, or Introduction, is an introduction to logic and philosophy, and in its Latin translation was the standard textbook on logic throughout the Middle Ages. In addition, through several of his works, most notably Philosophy from Oracles and Against the Christians, he was involved in a controversy with a number of early Christians, and his commentary on Euclid's Elements was used as a source by Pappus of Alexandria.