De Spiritu Sancto (Of the Holy Spirit‪)‬

Basil of Caesarea, also called Saint Basil the Great, (330 –379) was the bishop of Caesarea Mazaca in Cappadocia, Asia Minor (modern-day Kayseri, Turkey).  St. Basil was born into the wealthy family of Basil the Elder, a famous rhetor, and Emmelia of Caesarea. His parents were known for their piety, and his maternal grandfather was a Christian martyr, executed in the years prior to Constantine I's conversion.

Theologically, Basil was a supporter of the Nicene faction of the church, in opposition to Arianism on one side and the followers of Apollinaris of Laodicea on the other. His ability to balance his theological convictions with his political connections made Basil a powerful advocate for the Nicene position.

In addition to his work as a theologian, Basil was known for his care of the poor and underprivileged. Basil established guidelines for monastic life which focus on community life, liturgical prayer, and manual labor. Together with Pachomius he is remembered as a father of communal monasticism in Eastern Christianity. He is considered a saint by the traditions of both Eastern and Western Christianity.

Basil, Gregory of Nazianzus, and Gregory of Nyssa are collectively referred to as the Cappadocian Fathers. The Eastern Orthodox Church and Eastern Catholic Churches have given him, together with Gregory of Nazianzus and John Chrysostom, the title of Great Hierarch. The Eastern Orthodox Church and the Roman Catholic Church have also named him a Doctor of the Church. He is also referred to as "the revealer of heavenly mysteries" (Ouranophantor).

The principal theological writings of Basil are his De Spirity Sancto (On the Holy Spirit), a lucid and edifying appeal to Scripture and early Christian tradition (to prove the divinity of the Holy Spirit), and his Refutation of the Apology of the Impious Eunomius, written in 363 or 364, three books against Eunomius of Cyzicus, the chief exponent of Anomoian Arianism. The first three books of the Refutation are his work; the fourth and fifth books that are usually included do not belong to Basil, or to Apollinaris of Laodicea, but probably to Didymus "the Blind" of Alexandria.