Not until Augustine of Hippo was there ANYONE among the Latin fathers who taught or even suggested the filioque heresy. It is therefore a novelty and thus heresy, if only because of that. This too was been covered with great thoroughness by St. Mark of Ephesus at the Council of Florence. The Latin bishops there had no reponse to make other than scholastic proofs as opposed to patristic evidence. Don't take my word for it. Read Ostroumoff's history of the council.
Yet how can I, who derive the Son from no alien source, but from the Father's substance, who say he does nothing without the Father's will and that he has received from the Father all authority - how can I in the matter of the faith be destroying that monarchy which I say has been delivered by the Father to the Son and is conserved in the Son? Let this be taken to apply also to the third sequence, for I reckon the Spirit from nowhere else than from the Father through the Son. ...For God brought forth the Word, as also the Paraclete teaches, as a root brings forth the ground shoot, and a spring the river, and the sun its beam: for these manifestations also are "projections" of those substances from which they proceed. You need not hesitate to say that the shoot is son of the root and the river son of the spring and the beam son of the sun, for every source is a parent and everything that is brought forth from a source is its offspring - and especially the Word of God, who also in an exact sense has received the name of Son: yet the shoot is not shut off from the root nor the river from the spring nor the beam from the sun, any more than the Word is shut off from God. Therefore according to the precedent of these examples I profess that I say that God and his Word, the Father and his Son, are two: for the root and the shoot are two things, but conjoined; and the spring and the river are two manifestations, but undivided; and the sun and its beam are two aspects, but they cohere. Everything that proceeds from something must of necessity be another beside that from which it proceeds, but it is not for that reason separated from its. But where there is a second one there are two, and where there is a third there are three. For the Spirit is third with God and his Son, as the fruit out of the shoot is third from the root, and the irrigation canal out of the river third from the spring, and the illumination point out of the beam third from the sun: yet in no respect is he alienated from that origin from which he derives his proper attributes. In this way the Trinity, proceeding by intermingled and connected degrees from the Father, in no respect challenges the monarchy, while it conserves the quality of the economy. ...
Remember at every point that I have professed this rule, by which I testify that Father and Son and Spirit are unseparated from one another, and in that case you will recognise what I say and in what sense I say it. For look now, I say that the Father is one, and the Son another, and the Spirit another (every unlearned or self-willed person takes this statement in bad part, as though it proclaimed diversity and because of diversity threatened a separation of Father and Son and Spirit: but I am bound to make it, so long as they maintain that Father and Son and Spirit are identical, favouring the monarchy at the expense of the economy), not however that the Son is other than the Father by diversity, but by distribution, not by division but by distinction, because the Father is not identical with the Son, they even being numerically one and another. For the Father is the whole substance, while the Son is an outflow and assignment of the whole, as he himself professes, Because my Father is greater than I: and by him, it is sung in the psalm, he has also been made less, a little on this side of the angels. So also the Father is other than the Son as being greater than the Son, as he who begets is other than he who is begotten, as he who sends is other than he who is sent, as he who makes is other than he through whom a thing is made. It suits my case also that when our Lord used this word regarding the person of the Paraclete, he signified not division but ordinance: for he says, I will pray the Father and he will send you another advocate, the Spirit of truth. Thus the calls the Paraclete other than himself, as we say the Son is other than the Father, so as to display the third sequence in the Paraclete as we the second in the Son, and so to preserve the economy. (Tertullian, Adversus Praxean, 4, 8-9)
Concerning the Holy Spirit I ought not to be silent, and yet I have no need to speak; still, for the sake of those who are in ignorance, I cannot refrain. There is no need to speak, because we are bound to confess Him from the Father and the Son as authors. For my own part, I think it wrong to discuss the question of His existence. (St. Hilary of Poitiers, De Trinitate, II, 29)But, for my part, I cannot be content by the service of my faith and voice, to deny that my Lord and my God, Thy Only-begotten, Jesus Christ, is a creature; I must also deny that this name of ‘creature’ belongs to Thy Holy Spirit, seeing that He proceeds from Thee and is sent through Him, so great is my reverence for everything that is Thine. Nor, because I know that Thou alone art unborn and that the Only-begotten is born of Thee, will I refuse to say that the Holy Spirit was begotten, or assert that He was ever created. I fear the blasphemies which would be insinuated against Thee by such use of this title ‘creature,’ which I share with the other beings brought into being by Thee. Thy Holy Spirit, as the Apostle says, searches and knows Thy deep things, and as Intercessor for me speaks to Thee words I could not utter; and shall I express or rather dishonour, by the title ‘creature,’ the power of His nature, which subsists eternally, derived from Thee through Thine Only-begotten? ...
As in the revelation that Thy Only-begotten was born of Thee before times eternal, when we cease to struggle with ambiguities of language and difficulties of thought, the one certainty of His birth remains; so I hold fast in my consciousness the truth that Thy Holy Spirit is from Thee and through Him, although I cannot by my intellect comprehend it. (St. Hilary of Poitiers, De Trinitate, XII, 55)
If Augustine was the originator of the doctrine, one wonders how it should have been established so quickly in the East. To quote just a few witnesses: Henri Crouzel (Origen) comments on Origen's view of the Holy Spirit in the following passage:
Another important passage about the Holy Spirit is to be found in the Commentary of John. Its starting point is in John 1, 3: ‘All things were made by him (= the Word)’. Three opinions are then put forward: either the Holy Spirit owes his existence to the Word, being included in these ‘all things’; or He does not so owe it, being without origin; or He has not really an existence of his own (ousia idia) different from that of the Father and the Son: this last solution is modalist, and Origen embraces the first one. So there are three subsistant realities (hypostases, identical with ousia idia), the Father, the Son and the Holy Spirit, and - this is his answer to the second hypothesis - only the Father is without origin. The Spirit is then the highest of the beings that come from the Father by the Son: that is why He is not called a Son. Only the Son is son by nature and the Holy Spirit needs the intermediary function of the Son to subsist individually, and also to be wise, intelligent, just and all that He is and share in all the epinoiai of the Son. One cannot make of the word egeneto in John 1, 3 (‘was made’) a pretext for claiming that the Spirit is for Origen a creature: that would be to forget what we have said above about the interchangeability before Nicaea of the verbs gignomai and gennao as well as their derivatives with one n or two, to signify creation or generation.
Didymus the Blind says, in his book on the Holy Spirit:
So too the Son is said to receive from the Father the very things by which he subsists. For neither has the Son anything else except those things given him by the Father, nor has the Holy Spirit any other substance than that given him by the Son.
St. Gregory of Nyssa says, in his book against the heretic Eunomius (I, §42):
On the one hand, because the existence of the Son is not marked by any intervals of time, and the infinitude of His life flows back before the ages and onward beyond them in an all-pervading tide, He is properly addressed with the title of Eternal; again, on the other hand, because the thought of Him as Son in fact and title gives us the thought of the Father as inalienably joined to it, He thereby stands clear of an ungenerate existence being imputed to Him, while He is always with a Father Who always is, as those inspired words of our Master expressed it, “bound by way of generation to His Father’s Ungeneracy.” Our account of the Holy Ghost will be the same also; the difference is only in the place assigned in order. For as the Son is bound to the Father, and, while deriving existence from Him, is not substantially after Him, so again the Holy Spirit is in touch with the Only-begotten, Who is conceived of as before the Spirit’s subsistence only in the theoretical light of a cause.
St. Basil says, in his own refutation of Eunomius:
Even if the Holy Spirit is third in dignity and order, why need he be third also in nature? For that he is second to the Son, having his being from him and receiving from him and announcing to us and being completely dependent on him, pious tradition recounts; but that his nature is third we are not taught by the Saints nor can we conclude logically from what has been said ...
This testimony, we may note, was so strong that it was erased from some Greek codices - and Mark refused to believe it was authentic, since it was utterly fatal to his position. Bessarion, however, visiting Constantinople before the sack, even found copies in which this had been erased and substituted with a new text, which had been upheld by Mark at Florence. Fr. Gill comments on this:
Bessarion wrote at some length on the first of these in his letter to Alexius Lascaris, where he says that there were six codices in all of the Adversus Eunomium in Florence, five of which were against and one for Mark's contention, and that he took the opportunity of his return to Constantinople immediately after the Council to check by manuscripts there. He examined as far as he could all the manuscripts of all the Constantinopolitan monasteries and found that the more ancient codices had the text of the Latins and the more recent ones that upheld by Eugenicus, and what is more significant, that two codices, both ancient, one of them dated some 350 years before, had the Latin 'additions', in the one case badly erased so that they were still visible, in the other inked over (P. G. 161, 324-8).
To continue - St. Athanasius bears witness to the doctrine in many places. In his book to Serapion, we find:
Insofar as we understand the special relationship of the Son to the Father, we also understand that the Spirit has this same relationship to the Son. And since the Son says, "everything that the Father has is mine", we will discover all these things also in the Spirit through the Son.
Elsewhere, in his Discourses Against the Arians, he says (III, §24):
What then is our likeness and equality to the Son? rather, are not the Arians confuted on every side? and especially by John, that the Son is in the Father in one way, and we become in Him in another, and that neither we shall ever be as He, nor is the Word as we; except they shall dare, as commonly, so now to say, that the Son also by participation of the Spirit and by improvement of conduct became Himself also in the Father. But here again is an excess of irreligion, even in admitting the thought. For He, as has been said, gives to the Spirit, and whatever the Spirit hath, He hath from the Word.
Now are these Fathers influenced by Augustine, even though they predate him? I should think not.
One wonders, for instance, whether the Council of Seleucia, held in 410 by Persian bishops, was suffering from Augustinian influence:
We confess a Living and Holy Spirit, the Living Paraclete Who is from the Father and from the Son, and one Trinity, one essence, one will, embracing the faith of the three hundred and eighteen bishops which was defined in the city of Nice. Such is our confession and our faith, which we have received from our holy Fathers.
This too was been covered with great thoroughness by St. Mark of Ephesus at the Council of Florence.
John of Montenero flattened Mark at the Council on precisely this matter. Mark's own words are the following:
The words of the western Fathers and Doctors, which attribute to the Son the cause of the Spirit, I never recognize (for they have never been translated into our tongue nor approved by the Oecumenical Councils) nor do I admit them, presuming that they are corrupt and interpolated ...
The Latin bishops there had no reponse to make
Funny, perhaps you're thinking of the Greeks.
Bessarion: So the Saints who taught the Filioque are heretics! The western and the eastern Saints do not disagree, for the same Spirit spoke in all the Saints. Compare their works and they will be found harmonious.Mark: But who knows if the books have not been falsified by them?
Bessarion: If we remove all such words from the books -- whole homilies, commentaries on the Gospels, complete treatises on trinitarian theology ---there will be nothing left but blank pages.
Bessarion himself comments:
They brought forward passages not only of the western teachers but quite as many of the eastern... to which we had no reply whatsoever to make except that they were corrupt and corrupted by the Latins. They brought forward our own Epiphanius as in many places clearly declaring that the Spirit is from the Father and the Son: corrupt we said they were. They read the text mentioned earlier in Basil's work against Eunomius: in our judgment it was interpolated. They adduced the words of the Saints of the West: the whole of our answer was 'corrupt' and nothing more. We consider and consult among ourselves for several days as to what answer we shall make, but find no other defence at all but that...We had no books that would prove the Latin texts to be corrupt, no Saints who spoke differently from those put forward. We found ourselves deprived of a just case in every direction. So we kept silent.
Okay, I won't.
Concerning the Holy Spirit, I ought not to remain silent, nor yet is it necessary to speak. Still, on account of those who do not know Him, it is not possible for me to be silent. However it is necessary to speak of Him who must be acknowledged, who is from the Father and the Son, His Sources.
St. Hilary of Poitiers, The Trintiy, 2, 29 (AD 356 to 359)"The Holy Spirit when he proceeds from the Father and the Son, does not separate himself from the Father and does not separate himself from the Son"
St. Ambrose, The Holy Spirit, 1, 11, 120, AD 381)Following, therefore, the form of these examples, I profess that I do call God and His Word, - the Father and His Son, - two. For the root and the stem are two things, but conjoined; the fountain and the river are two kinds, but indivisible; the sun and the ray are two forms, but coherent ones. Anything which proceeds from another must necessarily be a second to that from which it proceeds; but it is not on that account separated from it. Where there is second, however, there are two; and where there is third, there are three. The Spirit, then, is third from God and the Son, just as the third from the root is the fruit of the stem, and third from the fountain is the stream from the river, and third from the sun is the apex of the ray.
Tertullian, Against Praxeas, 8, 5 (about AD 213)
Perhaps these three (among others) fell into a time warp from after St. Augustine and came to dwell before him? Otherwise, its unclear how no one preached the filioque until St. Augustine when many preached it before him.