Diogenes of Sinope
He was a native of Astypalaia, and it was probably to this island origin that he owed the nautical skills which would prove so advantageous to him. He was a disciple of Diogenes of Sinope, the Cynic philosopher. Diogenes Laërtius also calls him "Onesicritus of Aegina", and says that he came to Athens because his two adult sons, Androsthenes and Philiscus, were attracted to the philosophy of Diogenes the Cynic, whence Onesicritus also became an ardent disciple. If so, he must have been already advanced in years when he joined the expedition of Alexander.