I wrote this post and drew this illustration for Facebook a few days ago but I think it’s germane to this OP:
An illustration I made showing the spiration of the Spirit from the Father and through the Son.
Showing how the Filioque is a 100% Orthodox Catholic doctrine, and that Eastern/Oriental Orthodox Christians who take issue with it are making a mistake.
“[There is] one Holy Spirit, having substance from God, and who is manifested through the Son; image of the Son, perfect of the perfect; life, the cause of living; holy fountain; sanctity, the dispenser of sanctification; in whom is manifested God the Father who is above all and in all, and God the Son who is through all. Perfect Trinity, in glory and eternity and sovereignty neither divided nor estranged”
-St. Gregory the Thaumaturge (Confession of Faith [A.D. 265]).
“Concerning the Holy Spirit . . . it is not necessary to speak of him who must be acknowledged, who is from the Father and the Son, his sources”
-St. Hilary of Poitiers (The Trinity 2:29 [A.D. 357]).
"The Latin tradition of the Creed confesses that the Spirit “proceeds from the Father and the Son (filioque)”. The Council of Florence in 1438 explains: “The Holy Spirit is eternally from Father and Son; He has his nature and subsistence at once (simul) from the Father and the Son. He proceeds eternally from both as from one principle and through one spiration. . . . And, since the Father has through generation given to the only-begotten Son everything that belongs to the Father, except being Father, the Son has also eternally from the Father, from whom he is eternally born, that the Holy Spirit proceeds from the Son.”
The affirmation of the filioque does not appear in the Creed confessed in 381 at Constantinople. But Pope St. Leo I, following an ancient Latin and Alexandrian tradition, had already confessed it dogmatically in 447,76 even before Rome, in 451 at the Council of Chalcedon, came to recognize and receive the Symbol of 381. The use of this formula in the Creed was gradually admitted into the Latin liturgy (between the eighth and eleventh centuries). The introduction of the filioque into the Niceno-Constantinopolitan Creed by the Latin liturgy constitutes moreover, even today, a point of disagreement with the Orthodox Churches.