Having thought a bit more about the RC Catechism's assertions of the Filioque, and having thought more about the contradictions inherent in the text of the Catechism itself, I'm beginning to think that a/ most Catholics do not understand what is being said when they say that Spirit proceeds from both the Father and the Son (Catholics I talk to are thinking in a completely different channel), and b/ the Catechism itself often seems to be a "compromise" document trying to stitch together elements that do not really belong with each other.
Anyway, given that the main objection to the Filioque is that it diminishes the role of the Holy Spirit, relegating Him from being a co-equal member of the Holy Trinity to that of a subordinate servant of the Holy Duet of Father and Son, then it is obviously worth while examining the writings of Orthodox Church Fathers who, though not dealing directly with the Filioque issue, explain the nature and role of the Holy Spirit in a way that shows the real, dynamic equality of the Spirit with Father and Son.
Mor Moses Bar Kepho (d901) the Syriac Orthodox Bishop of Mosul wrote a
lengthy "Exposition of the Mysteries" in which he emphasises that the Holy Spirit is called Holy "because there are many spirits", and that, since there also other holy spirits (the angels), then the reality of who the Holy Spirit is must be made precise. The Holy Spirit is "the Lord, the life giver.
That is: this Spirit is Lord; and moreover, He bestows life on all the angels, and on all that live. Equal in essence: that is, He also has another
property which distinguishes Him from all other holy spirits. And what is this? And we say, that He is equal in essence and in Godhead to the Father and the Son..."
That the Holy Spirit is no ordinary agent or messenger is confirmed when Moses Bar Kepho explains the role of the Holy Spirit in the Incarnation of the Logos and in the transformation of the elements during the Liturgy.
"Concerning the calling of the Holy Spirit.
It is right that we enquire here concerning the Holy Spirit, why He comes
down upon the bread and wine which are set upon the altar. We know that
the Son comes down upon the bread and wine and is united to them
hypostatically: but the Holy Spirit, why does He come down? We say, for this reason: as He came down into the womb of the Holy Virgin Mary... and made the body which was from the Virgin the body of God the Word,
so He comes down upon the bread and wine which are upon the altar and makes them that body and blood of God the Word which was from the Virgin. Again we say thus: just as in the case of the Holy Virgin Mary the Father willed that the Son should become incarnate, that the Son came down into the womb of the Virgin and became,and the Spirit also came down
into the womb of the Virgin and caused the Son to be incarnate of her, so here also in the case of the altar the Father wills that the Son be united
hypostatically to the bread and wine that they become His body and blood, so the Son comes down that He may be hypostatically united to them, and the Spirit also comes down that He may unite them to Him, even as He caused Him to be incarnate of the Virgin."
To further underline the vivifying activity of the Holy Spirit, Moses Bar Kepho explains why, during the Liturgy, the priest makes the sign of the Cross three times over the transformed bread and wine:
The first time to "make known that the Father indeed wills, that the
Son consents, and the Spirit sanctifies. By the second time.. that the
Father wills, the Son consents, and the Spirit completes. By the third
time... that the Father wills, the Son consents, and the Spirit perfects."
It is obvious here that the Holy Spirit cannot be a subordinate agent. More precisely Moses Bar Kepho shows that while the Son consents (submits)
to the will of the Father the Spirit sanctifies, completes and perfects the will of the Father, proceeding, therefore, not from both the Father and the Son, but from the Father alone.