St. Augustine on the Filioque

Here is the Filioque defined by the ecumenical council of Florence (1439): “…the holy Spirit is eternally from the Father and the Son, and has his essence and his subsistent being from the Father together with the Son, and proceeds from both eternally as from one principle and a single spiration. We declare that when holy doctors and fathers say that the holy Spirit proceeds from the Father through the Son, this bears the sense that thereby also the Son should be signified, according to the Greeks indeed as cause, and according to the Latins as principle of the subsistence of the holy Spirit, just like the Father. And since the Father gave to his only-begotten Son in begetting him everything the Father has, except to be the Father, so the Son has eternally from the Father, by whom he was eternally begotten, this also, namely that the holy Spirit proceeds from the Son. We define also that the explanation of those words ‘and from the Son’ was licitly and reasonably added to the creed for the sake of declaring the truth and from imminent need.”

Some scriptures showing Filioque are Gal. 4:6: "...God hath sent the Spirit of his Son into your hearts...", and Apc. 22:1: "And he shewed me a river of water of life, clear as crystal, proceeding from the throne of God and of the Lamb." We also know that "the Son cannot do any thing of himself, but what he seeth the Father doing: for what things soever he doth, these the Son also doth in like manner (Jn. 5:19)." So (1) the Son can do nothing of Himself, meaning what the Father does eternally the Son does also, and (2) the Son does in like manner what the Father does. So if the Spirit proceeds from the Father eternally, then the Son will (1) do it with him and (2) do it in the same manner. Moreover, all that the Father has are His (Jn. 16:15), and if the Father has the Spirit, so does the Son. Thus it can be said that the Spirit is "of" the Son and "from" the Son. However, we ought not to think that the Son is along with the Father the origin of all divinity, for the same council says that "since the Father gave to his only-begotten Son in begetting him everything the Father has, except to be the Father, so the Son has eternally from the Father, by whom he was eternally begotten, this also, namely that the holy Spirit proceeds from the Son." An example of the Son being begotten of the Father is Jn. 3:16.

St. Augustine affirmed the Filioque by calling the Spirit "of the Father and of the Son." The following are quotes from On the Trinity, a.k.a. De Trinitate.

-     "...and the Holy Spirit is neither the Father nor the Son, but only the Spirit of the Father and of the Son..."

-     "...He is the Spirit both of the Father and of the Son."

-     "Neither is the Spirit of either thence excluded, that is, the Spirit of the Father and of the Son; which Holy Spirit is specially called the Spirit of truth...[Jn. 14:6]"

Prayer for the Eastern "Orthodox"

Pater noster, qui es in caelis. Sanctificetur nomen Tuum. Adveniat regnum Tuum. Fiat voluntas Tua, sicut in caelo et in terra. Panem nostrum quotidianum da nobis hodie. Et dimitte nobis debita nostra, sicut et nos dimittimus debitoribus nostris. Et ne nos inducas in tentationem, sed libera nos a malo.

Ave Maria, gratia plena, Dominus tecum. Benedicta tu in mulieribus, et benedictus fruictus ventris tui Jesus. Sancta Maria, mater Dei, ora pro nobis pecatoribus, nunc, et in hora mortis nostrae.

Lord, come to the help of those struggling with finding the true faith and especially those who are Eastern Orthodox, for they are so close to the truth but still reject it. O Good Father, for the sake of Thy great mercy, help them. Through Christ our Lord. Amen. St. Augustine, pray for us.

Sources

Florence: https://www.papalencyclicals.net/councils/ecum17.htm, Augustine: https://www.newadvent.org/fathers/130101.htm