PHANIAS, of Eresus in Lesbos, Greek philosopher, important as an immediate follower of and commentator on Aristotle, came to Athens about 332 B.C., and joined his compatriot, Theophrastus, in the Peripatetic school. He wrote works entitled Analytica, Categoriae and De interpretatione, which were either paraphrases or critical commentaries, and seem to have added little to Aristotle's own writings. Alexander of Aphrodisias refers to a work πρὸς Διόδωρον, and Athenaeus quotes from another treatise, Against the Sophists. Outside philosophy, he and Theophrastus carried on the physical investigations of Aristotle, Athenaeus frequently quotes from a work on botany which manifests great care in definitions and accuracy of observation. From Plutarch (Life of Themistocles) we learn that he was regarded as an historian of importance. The chief of his historical works is the Prytaneis Eresii, which was either a history of his native place or a general history of Greece arranged according to the period of the Eresian magistracy. He wrote also works on the Tyrants of Sicily and on tyranny in general. The value of these books is attested by the frequency with which they are quoted on questions of chronology (e.g. by Plutarch, Suidas, Athenaeus). To the history of Greek literature he contributed works on the poets and on the Socratics, both of which are quoted.
He must be distinguished from another Phanias, a Stoic philosopher, disciple of Posidonius. Diogenes Laertius mentions a work of his wherein he compares Posidonius with Panaetius in arguing from physical principles.