Filioque “is a Latin term (‘and from the Son’) added to the original Niceno-Constantinopolitan Creed (commonly known as the Nicene Creed), and which has been the subject of great controversy between Eastern and Western Christianity.” [Wikipedia]
As has happened many times in the history of the Church, controversies over doctrine have led the Magisterium to clarify the teachings of the Faith, leading to new dogmas. These “new” dogmas were always found, at least implicitly, in the sacred deposit of faith (Sacred Tradition and Sacred Scripture). The truths of Tradition and Scripture on faith and morals are material dogma, and when such a truth is taught infallibly by the Magisterium, it becomes also formal dogma. The Filioque clause in the Creed is formal dogma. The fact that earlier Creeds did not contain that clause, but simply said that the Holy Spirit proceeds “from the Father” does not refute the addition of “and from the Son” (filioque) to the description of the procession of the Spirit. Rather, it is a common case of clarification of doctrine over time.
Why is it true that the Spirit proceeds from the Father and from the Son? Is it possible that the Spirit might proceed only from the Father? What is the difference between the Father, the Son and the Holy Spirit?
Each Person of the most holy Trinity is “consubstantial”. This means that whatever is true of the Divine Nature, is true of each Person of the Trinity. For each of the three Persons fully possesses the one Nature. The Divine Nature is the substance of God, and so consubstantial means that each Person has the same substance or nature.
God is love. Therefore, the Father is love, the Son is love, the Spirit is love. And the same is true for the other aspects of the Nature of God. God is all-knowing, God is inherently good, God is eternal, God is all-powerful, etc. Whatever is truly said of the Nature is said truly of each Person of the Trinity.
There can be only one God, i.e. one Divine Nature. God is infinite eternal perfect existence. If there were, hypothetically, two Gods, what would be the difference between them? If the one God were infinite eternal perfect existence, a second God could not be the same, as there would be no difference whatsoever between them, thereby proving that there is only one God. Infinite eternal perfection of existence itself leaves no room for a second infinite eternal perfect existence, as the first encompasses all that can be infinite eternal perfect existence. So there cannot be more than one God.
How then can there be three Persons, if each fully possesses the one Divine Nature which is infinite eternal perfect existence? They are distinguished by procession:
The Father does not proceed.
The Son proceeds only from the Father.
The Holy Spirit proceeds from the Father and from the Son (as one spiration, not a double procession).
The relation between the Persons, based on procession, is the distinction that allows there to be three Persons. Otherwise, without this distinction, we would have the same problem as the proposal of more than one God. A second or third God would be in no way different from the one God, neither by time, nor place, nor nature. And so more than one God cannot possibly exist.
This problem does not occur with the Trinity as each Person has a unique relationship to the other two Persons, based on procession.
The Son is called Son because He proceeds only from the Father. He is called Word because it is as if the Father spoke a single Word, which is the fullness of His own Person — except for the difference of procession. All that the Son is, is from the Father. The Son owes all that He is as a Person to the Father.
The Holy Spirit proceeds from the Father and from the Son, but as one act. This procession is called spiration, after the relation of the Spirit to the other two Persons. All that the Spirit is, is from the Father and Son. The Holy Spirit owes all that He is as a Person to the Father and the Son.
What if the Spirit proceeded only from the Father? Then the Spirit would be no different from the Son. Then the Spirit would be called “Son” or “Word”, contrary to Tradition and Scripture. There would be no difference at all between the Son and the Spirit, if the Holy Spirit proceeded only from the Father.
In order that there be distinctions between the three Persons, especially between the Son and the Holy Spirit, the Spirit must be understood to proceed from both the Father and the Son. Without the Filioque clause, the Spirit would be no different from the Son, and so would not exist. There cannot be two Sons in the Trinity, for the same reason that there cannot be two Gods. It is not that the three Persons are each Gods; that claim would be heresy. Rather, for there to be three Persons, each Person must be different from the other. And that difference is found solely in procession. There cannot be two Sons or two Words in the Trinity, and so the Spirit cannot proceed only from the Father.
Therefore, in order for Eastern Orthodox Catholics to be eventually united in one Church with the Latin Rite and Eastern Rite Catholics, they must accept the filioque clause and the other dogmatic teachings of the one holy catholic and apostolic Church.
Ronald L. Conte Jr.