Three councils—indeed, one council and two “conciliabules”—were held in Ancyra in the fourth century.
The council that met between Easter and Pentecost in 314 was of great importance and assumed almost the character of a plenary council of the Churches of Asia Minor and Syria; it issued twenty-five disciplinary canons, chiefly concerning the treatment of the “lapsi” of the last persecution (cf. Mansi, II, pp. 513–40). All were incorporated into the canonical law of the Byzantine Church by the Council in Trullo (691) and thus enjoyed the good fortune of being commented upon by the great canonists of the twelfth century (PG 137, 1123–1106).
In 358, at the instigation of George of Laodicea—one of the principal partisans of the Semi-Arians—a new synod was convened in Ancyra under the presidency of Basil of Ancyra to react against the second Council of Sirmium held in 357, where the transgressing Arians, the so-called Anomeans, had triumphed. At the conclusion of its proceedings, a lengthy letter was drawn up in which the doctrine of the Semi-Arians, also called “Homoiousians,” was set forth.
In the winter of 375 another conciliabulum was held in Ancyra, at which the deposition of Hypsis, the Catholic bishop of Parnassus, was decreed, and a calumnious accusation was lodged against St Gregory of Nyssa, against whom an order for arrest was issued (though the saint managed to escape the soldiers’ hands).
The letter of the Synod of 358 is preserved in full by St Epiphanius, Haeres., 73, 2–11, and in part by St Hilary, De Synodis, 12–25, 88–91, who gives an orthodox interpretation of II. Cf. also: Hefele-Leclercq, I, pp. 903–908; G. Rasneur, L’homoiousianisme dans ses rapports avec l’orthodoxie, in Revue d’histoire ecclésiastique, 4 (1903), p. 201.
The conciliabulum of 375 is known to us only through St Basil’s letters 225, 237–40, 244. Hefele makes no mention of II. See what Tillemont says of it, IX, Paris 1703, pp. 247–49.