Why celebrate Corpus Christi today, the Thursday after the Feast of the Most Holy Trinity? Are we not detracting from the unity of the liturgical year, undermining 'Ordinary Time' and irrationally repeating the theme of our Maundy Thursday observance?
For those who reject Corpus Christi as a medieval innovation, it is worth noting that Trinity Sunday is a similar medieval innovation. It was in the early 14th century that Pope John XXII instructed the Western Church to observe the Feast of the Trinity on the Sunday after Pentecost. Corpus Christi actually predates Trinity Sunday by half a century, sanctioned by Pope Urban IV in 1264.
Both feasts enable the Church to prayefully reflect upon the conclusion of the Paschal season and the observance of the Advent-Pentecost cycle. First on Trinity Sunday, we confess that it is the Triune God who has wrought our salvation in Incarnation, Epiphany, Cross, Resurrection, Ascension and Pentecost. Then, today, we proclaim that it is in the Holy Eucharist that this salvation is made present amongst us - and that the Eucharist witnesses to how the Triune God saves His creation.
It is the consistent witness of the Fathers that it is in the Eucharist that the Church experiences and confesses the saving dynamic of the Incarnation:
[Against the Docetics] They abstain from the Eucharist and from prayer, because they confess not the Eucharist to be the flesh of our Saviour Jesus Christ, which suffered for our sins, and which the Father, of His goodness, raised up again - St. Ignatius of Antioch;
We do not consume the eucharistic bread and wine as if it were ordinary food and drink. We have been taught that just as Jesus became a human being of flesh and blood by the power of the Word of God for our salvation, so also the food that our flesh and blood assimilate for their nourishment becomes the flesh and blood of this Jesus - St. Justin Martyr;
[Against the Gnostics] They are totally foolish, these people who despise the whole saving plan of God, who deny the salvation of the flesh, and scorn its regeneration, claiming it is not capable of incorruptibility. If the flesh is not saved, the Lord did not redeem us by His Blood, the cup of the Eucharist is not communion with His Blood, and the bread we break is not communion in His Body - St.Irenaeus.
In our celebration of Corpus Christi, we affirm the flesh-and-blood reality, the very earthiness, of the redemption upon which we have meditated since Advent Sunday. God in real flesh and blood, in the manger, in the Jordan River, in the Garden, on the wood of the Cross, in the Tomb, Risen, Ascended, Glorified. And in the Eucharist.
It is for this reason that Richard Hooker famously situates his reflection on the Church's sacramental economy within an extended meditation on the Incarnation (see LEP V, 50-56). This leads to one of the most beautiful passages in the Lawes:
It is too cold an interpretation, whereby some men expound our being in Christ to import nothing else, but only that the self same nature, which makes us to be men, is in him, and makes him man as we are. For what man in the world is there which has not so far forth communion with Jesus Christ? It is not this that can sustain the weight of such sentences as speak of the mystery of our coherence with Jesus Christ. The Church is in Christ as Eve was in Adam. Yes, by grace we are every one of us in Christ and in his Church, as by nature we are in those our first parents. God made Eve of the rib of Adam. And his Church he frames out of the very flesh, the very wounded and bleeding side of the Son of Man. His body crucified and his blood shed for the life of the world, are the true elements of that heavenly being, which makes us such as himself of whom we come (V 56.7).
It is in the Eucharist that the Church experiences and proclaims "the mystery of our coherence with Jesus Christ" - the gift of the grace lavished upon us by the Triune God in Incarnation, Cross, Resurrection, Ascension and Pentecost. Flesh is saved by flesh. By the flesh and blood of the Son of God we in our flesh and blood participate in the communion of the Holy Trinity.
By celebrating Corpus Christi, the Church is renewed in the scandal of the Incarnation. It is not just the world that adheres to flesh-denying narratives of the Docetics and the Gnostics. Too often we in the Church collude with such narratives. Corpus Christi beautifully but forcefully reminds us that the plan of salvation we have celebrated is the salvation of this world, of our flesh, our bodies. For today we hear the Crucified and Risen One say, "those who eat my flesh and drink my blood abide me, and I in them".