(c.330–79 [or possibly slightly earlier]),
one of the three Cappadocian Fathers. The brother of St Gregory of Nyssa, he settled as a hermit near Neocaesarea in 358; he left his retirement only when called upon by his bishop to defend orthodoxy against the Arian Emp. Valens. In 370 he became Bp. of Caesarea in Cappadocia. This office involved him in controversies with the extreme Arian party led by Eunomius, as well as with the Pneumatomachi, who denied the Divinity of the Holy Spirit.
His writings include a large collection of letters, a treatise ‘On the Holy Spirit’, and three ‘Books against Eunomius’. With St Gregory of Nazianzus he compiled the ‘Philocalia’. He tried to reconcile the Semiarians to the formula of Nicaea and to show that their term ‘homoiousios’ (‘like in substance [to the Father]’) had the same implications as the Nicene ‘homoousios’ (‘of one substance’). The virtual termination of the Arian controversy after the Council of Constantinople of 381 is a tribute to his success. He possessed great talent for organization and impressed on E. monasticism the structure and ethos which it has retained ever since. Feast day in the W., 2 Jan. (formerly 14 June, as now in parts of the Anglican Communion); in the E., 1 Jan. See also following entries.