St. Basil was born about 330 at Caesarea in Cappadocia. He came from a wealthy and pious family which gave a number of saints, including his mother Saint Emily (also styled Emilia or Emmelia), grandmother Saint Macrina the Elder, sister Saint Macrina the Younger and brothers Saints Gregory of Nyssa and Peter of Sebaste. It is also a widely held tradition that Saint Theosebia was his youngest sister, who is also a saint in the Church.
While still a child, the family moved to Pontus; but he soon returned to Cappadocia to live with his mother's relations, and seems to have been brought up by his grandmother Macrina. Eager to learn, he went to Constantinople and spent four or five years there and at Athens, where he had the future emperor Julian for a fellow student and became friends with Gregory the Theologian. Both Basil and Gregory were deeply influenced by Origen and compiled an anthology of uncondemned writings of Origen known as the Philokalia (not to be confused with the later compilation of the same name).
It was at Athens that he seriously began to think of religion, and resolved to seek out the most famous hermit saints in Syria and Arabia, in order to learn from them how to attain enthusiastic piety and how to keep his body under submission by asceticism.
After this we find him at the head of a convent near Arnesi in Pontus, in which his mother Emily, now a widow, his sister Macrina and several other ladies, gave themselves to a pious life of prayer and charitable works. Basil sided with those who overcame the aversion to the homoousios in common opposition to Arianism, thus drawing nearer to Saint Athanasius the Great.
He was ordained presbyter of the Church at Caesarea in 365, and his ordination was probably the result of the entreaties of his ecclesiastical superiors, who wished to use his talents against the Arians, who were numerous in that part of the country and were favoured by the Arian emperor, Valens, who then reigned in Constantinople.
In 370 Eusebius, bishop of Caesarea, died, and Basil was chosen to succeed him. It was then that his great powers were called into action. Caesarea was an important diocese, and its bishop was, ex officio, exarch of the great diocese of Pontus. Hot-blooded and somewhat imperious, Basil was also generous and sympathetic. His zeal for orthodoxy did not blind him to what was good in an opponent; and for the sake of peace and charity he was content to waive the use of orthodox terminology when it could be surrendered without a sacrifice of truth.
With all his might he resisted the emperor Valens, who strove to introduce Arianism into his diocese, and impressed the emperor so strongly that, although inclined to banish the intractable bishop, he left him unmolested. To an imperial prefect, astonished at Saint Basil's temerity, he said, "Perhaps you have never before dealt with a proper bishop."
To save the Church from Arianism, Basil entered into connections with the West, and with the help of Athanasius, he tried to overcome its distrustful attitude toward the Homoousians. The difficulties had been enhanced by bringing in the question as to the essence of the Holy Spirit. Although Basil advocated objectively the consubstantiality of the Holy Spirit with the Father and the Son, he belonged to those, who, faithful to Eastern tradition, would not allow the predicate homoousios to the former; for this he was reproached as early as 371 by the Orthodox zealots among the monks, and Athanasius defended him.
His relations also with Eustathius were maintained in spite of dogmatic differences and caused suspicion. On the other hand, Basil was grievously offended by the extreme adherents of Homoousianism, who seemed to him to be reviving the Sabellian heresy.
He did not live to see the end of the unhappy factional disturbances and the complete success of his continued exertions in behalf of Rome and the East. He suffered from liver illness and his excessive asceticism seems to have hastened him to an early death. A lasting monument of his episcopal care for the poor was the great institute before the gates of Caesarea, which was used as poorhouse, hospital, and hospice.