When, therefore, that priestly and Apostolic order had approved opinions of this kind, brought forward from evangelical authority, by decree of the Council the administration of the East was enjoined upon Asterius and the rest who were with him, while that of the West was decreed to Eusebius. There was added indeed in that decree of the Council also a fuller disputation concerning the Holy Spirit, that He should be believed to be of the same substance and deity as the Father and the Son, and that nothing whatsoever in the Trinity should be said to be either created, or inferior, or posterior. But also concerning the difference of substances and subsistences his discourse was set in motion through Scripture. The Greeks call them ousiai and hypostaseis.
For some said that substance and subsistence seemed to be one and the same; and that, since we do not speak of three subsistences in God, neither ought we to speak of three substances. But others, to whom substance seemed to signify something far different from subsistence, said that substance designates the very nature and account of any thing, by which it consists; whereas subsistence shows of each person this very thing—that which exists and subsists. And therefore, because of the heresy of Sabellius, three subsistences must be confessed, since it would seem to signify, as it were, three subsisting persons, lest we give occasion for suspicion, as though we were followers of that faith which confesses the Trinity only in names, and not in things and subsistences.
But concerning the incarnation of the Lord also it was comprehended that the body which the Lord had assumed He had assumed neither without sense nor without soul. All these things being cautiously and moderately composed, each one went his way in peace.