Chapter XXII.—At that Time, the Doctrine of the Holy Ghost was agitated, and it was decided that he is to be considered Consubstantial with the Father and the Son.
A question was renewed at this juncture which had previously excited much inquiry and now more; namely, whether the Holy Ghost is or is not to be considered consubstantial with the Father and the Son.
Many contentions and debates ensued on this subject, similar to those which had been held concerning the nature of God the Word. Those who asserted that the Son is dissimilar from the Father, and those who insisted that He is similar in substance to the Father, came to one common opinion concerning the Holy Ghost; for both parties maintained that the Holy Ghost differs in substance, and that He is but the Minister and the third in point of order, honor, and substance. Those, on the contrary, who believed that the Son is consubstantial with the Father, held also the same view about the Spirit. This doctrine was nobly maintained in Syria by Apolinarius, bishop of Laodicea; in Egypt by Athanasius, the bishop; and in Cappadocia and in the churches of Pontus by Basil and Gregory. The bishop of Rome, on learning that this question was agitated with great acrimony, and that it of course was augmented daily by controversies, wrote to the churches of the East and urged them to receive the doctrine upheld by the Western clergy; namely, that the three Persons of the Trinity are of the same substance and of equal dignity. The question having been thus decided by the Roman churches, peace was restored, and the inquiry appeared to have an end.
Reproduced in full. Translation: Nicene and Post-Nicene Fathers, series 2, vol. 2 (Schaff and Wace, 1890), public domain (Public domain).