"the most precious of all these encounters was that with Arrian of Nicomedia"

This is Lucius Flavius Arrianius Xenophon (86-160 AD), the author of the "Anabasis of Alexander" (a panegyric of Alexander the Great, which is nonetheless historically important as it draws on sources now lost), "Discourses of Epictetus" (directly referred to here) and "Indica" (a discourse on India). He was Consul in 129 or 130 AD and subsequently served as Governor of Cappadocia. As part of the "Second Sophistic" (along with Herodes Atticus and Polemo of Laodicea) he presided over a renaissance of Hellenistic rhetoric and education in the first half of the 2nd Century AD.