DIX: "The doctrine of the full Deity of the Holy Ghost ... was defined in 381 against the teaching of Macedonius that the Holy Ghost is not God as the Father and Son are God, but is in some way subordinate and intermediate between God and creatures. There is nothing in the NT which clearly indicates that the Orthodox doctrine is certainly right, or which is irreconcilable with Macedonianism in some form. Even the baptismal formula of Mt 28:19 can scarcely be pressed (as it was pressed then) in such a sense, seeing that baptism "in the name of the Lord Jesus" only is scriptural, and so late as the ninth century was still an officially accepted alternative. S Athanasius and S Basil both raised the question of the Third Person, but their controversy was waged with those who had followed them against the Arians. They appealed, naturally, to Scripture and Tradition, and it is notorious how defective in substance their appeal is found to be when it is closely examined. It is also remarkable that in the works which they wrote to vindicate this doctrine both carefully avoid even once applying the decisive word "God" to the Holy Ghost, though in this they are but following earlier writers, even professed Trinitarians like Novatian, and the NT itself.
"S Gregory Nazianzen, "the theologian" par excellence for the East, under whose presidency the Oecumenical Council of 381 actually defined the doctrine, is explicit that there were but "few" who accepted it in his day, and that Athanasius was the first and almost the only doctor to whom God had vouchsafed light on this subject. Elsewhere he is even more devastatingly honest with the admission that while the NT plainly revealed the Godhead of the Son it no more than "hinted at" that of the Holy Ghost, which was now being plainly revealed in his own day. This is some distance from talk of "most certain warrants of Holy Scripture". It was neither Scripture nor Tradition which imposed the dogma of 381, defined by the most thinly attended and least unanimous of all the assemblies which rank as General Councils, but the living magisterium of the Church of that age.
"That the full doctrine of the Spirit's Godhead was then believed in some sense "everywhere" we may hope, though the evidence is not reassuring. That it had "always" been believed by some we may suppose, though the evidence is at least defective. That it had previously been believed "by all" is demonstrably untrue."
This piece by Dom Gregory Dix is to be read in conjunction with the recent post titled Argumentum ad hominem.