Basil became Bishop of Caesarea in 370 on Eusebius' death. An extensive range of Basil's writings survive, including over 300 letters and around fifty homilies. His ascetic corpus is foundational within Byzantine monastic literature. Basil's main dogmatic works are his Against Eunomius and his On the Holy Spirit. Basil's homilies on the Hexameron present a perfect example of the difficulty of reading Basil's philosophy. Basil also participates directly in ancient philosophical debate. The epistemological tensions revealed are dealt with at much greater length in Basil's Trinitarian works where questions of what we know when we speak of God press strongly. A great deal of Basil's thinking on the Trinity was worked out in response to Eunomius, sometime bishop of Cyzicus and proponent of the view that the Only-begotten Son is unlike God in substance. Basil's notion of shared substance clearly contains elements inherited from non-Christian philosophy. Basil also uses language for substance that appears to be inspired by Stoicism.