As the Church presently celebrates the Feast of the Most Holy Trinity (the first Sunday after Pentecost in both the "ordinary" and "extraordinary" forms of the Roman Rite), allow me to share some thoughts (assembled somewhat in haste from homilies and jottings over the years) on this, the central mystery of Christian faith, the mystery of God's Being.
From 1759 until the introduction of the Missal of Paul VI it has been specified that in the Roman Rite the eucharistic Preface should be that of the Holy Trinity on all Sundays of the year. (In practice, this was not always the case.) This hymn in praise of the mystery of God's essence dates from the early Middle Ages. It is clear and unequivocal on the interrelation of the three divine Persons, insofar as their mutual and perfect possession of the divine nature, or "Godhead," is concerned. The Lord who is holy Father, almighty and eternal God, is fittingly and justly praised, says the opening phrase of the Preface. We address ourselves to God the Father telling Him that always and everywhere we offer thanksgiving - a eucharist - to Him,Who, together with Thine only-begotten Son and the Holy Ghost, art one God, one Lord: not in the Oneness of a single Person, but in the Trinity of one Substance. For what by Thy revelation we believe of Thy glory, the same do we believe of Thy Son, the same of the Holy Ghost, without difference or separation; so that in confessing the true and eternal Godhead, in It we should adore distinction in Persons, unity in Essence, and equality in Majesty: in praise of which Angels and Archangels, Cherubim also and Seraphim . . . [Baronius Press Daily Missal (1962), Summorum Pontificum Edition, 2007, p. 884]And so on, into the ceaseless chorus of praise that declares God to be thrice holy: Sanctus, Sanctus, Sanctus... It is all very orderly, almost like a mathematical equation, the truth of which is not immediately apparent but which is there nonetheless.
Yet it all bears little relation to the way we came to know the mystery of God's Being, which is at the same time the mystery of Christ. As the Preface of the Most Holy Trinity describes the mystery of divinity, it is more a doctrine to be held than an invitation to a new life. The prayer speaks of the central Christian mystery in such philosophical and non-biblical terms that we seem to have lost something precious in our relation to God, in our very attempts to describe who God is.
The sacred liturgy begins and ends with the sign of the cross made in the name of the Father, Son, and Holy Spirit. But how often do we think of ourselves as deeply and intimately related to each of the divine Persons, as adopted children of the Father precisely by reason of our union with the Son by the gift of the Spirit? It's been been said that if the doctrine of the Trinity had to be dropped as false, most Christians today would probably carry on their lives pretty much as before.
God's inner life is love, a union of giving among three Persons. The manifestation of love God makes in our behalf is a communication of the love that He Himself is. But we learn about God's trinitarian life only through being told how the Father means to make us His children in the only Son by the gift of the Holy Spirit. Without the gospel of Jesus Christ, we could never know God as Trinity, which is to say, we could never know God as love (cf. 1 John 4:16).
Down through the centuries, the Church deepened and refined her understanding of the mystery of God's own divine life. Numerous heresies triggered theological inquiry and debate, eventually enabling Christians to say that the Father eternally begets the Son, from whom in turn proceeds eternally the Holy Spirit. The Spirit comes from the Father and the Son (the phrasing here is that of the credal phrase of 5th century Spanish origin, Filioque; "from the Father through the Son," is the older formula, still used by the Eastern Catholic and Orthodox Churches). Unfortunately, in defining the trinitarian relations apart from those works of God in time (that is, apart from God's historical dealings with men), something was lost. I certainly don't suggest that the Church today cast aside her developed theology of processions and relations, her contemplation of God as He is in Himself. Rather, I'm saying that we need to recapture an earlier spirit which the New Testament and the primitive Roman liturgy stress, namely, God's work of Redemption as the best clue to the triune God who acts behind it. If the doctrine and liturgical feast of the Holy Trinity are to be something to us (which, in the first place, is why God disclosed the mystery to us), then the Redemption must be kept to the fore. Hence, the "theme" of Trinity Sunday, and indeed every Mass, is the atoning Sacrifice of Christ.
God has "rescued us from the power of darkness and transferred us into the kingdom of His beloved Son, in whom we have our redemption, the remission of our sins" (Col. 1:13f.) It is clear from this and other passages (Col. 1:27, 1 Cor. 3:16f., 15:20-44, etc.) that St Paul never conceived "the mystery of God" simply as the hidden or mysterious character of the Godhead. The mystery of God, for Paul, is Christ Himself (cf. Col. 2:2), God as He reveals His loving plan of salvation in Christ through the Holy Spirit.
The Christian life is essentially a trinitarian life. In baptism, that sacrament of faith which incorporates us into the mystical Body of Christ and so into the new relationships to Father, Son, and Holy Spirit, the very words designate the nature of this new life. The Christian is privileged to know God as He is in Himself, in His triunity, because the Word was made flesh. Christ is above all the revelation of the Father -- His Father is also our Father. The Father has predestined us from eternity to sonship in His only Son, a vocation given in virtue of Christ's life, death, resurrection and ascension. Through the power of the Holy Spirit -- the Spirit of Christ sent by Christ and the Father -- man is adopted as son; his new life of grace will be a journey to the Father, through the Son, in the Holy Spirit. Per ipsum [Christum], et cum ipso, et in ipso...
Having been made sharers of the divine nature through baptism, we now partake of God's life through faith and charity. The Father has first given the Son all that He (the Father) is, retaining only His relation of fatherhood as His personal distinction. The Son loves the Father perfectly, and this mutual love is personal: the Holy Spirit who proceeds from both Father and Son as from one source, by means of love. The Spirit is the bond of the mutual knowledge and self-giving of Father and Son.
All this is a communion of love. We are taken up into this Life by means of the sacred liturgy, starting with baptism. We are called to return to the Father through the Son in the Holy Spirit. As you listen to the stiff and precise language of the Preface this Trinity Sunday (sung or spoken, Latin or vernacular), bear in mind that, at bottom, it's all about Love -- the Love who created us, who destroyed death's power over us, and who calls us to an eternity of love with Himself.
