Tomorrow is the Solemnity of the Most Holy Body and Blood of Christ, commonly known as Corpus Christi. It is the day that Catholic celebrate the mystery of the Real Presence of Christ in the Eucharist. It is always the second Sunday after Pentecost (or the Sunday after Holy Trinity Sunday).
The dogma of the Real Presence is the belief that the elements of bread and wine are transformed into the Body and Blood of Jesus Christ. They are no longer bread and wine. They are entirely the Body and Blood of Jesus Christ. It is not that Christ is somehow present in the bread and wine, which is the Protestant belief called consubstantiation, meaning that Christ is present with (con) or within the substance of the bread and wine. Catholics believe in transubstantiation, meaning that the substance of the bread and wine are transformed into the Body and Blood of Jesus Christ. The Eucharistic elements are the Body and Blood of Christ.
This has been the faith of the Catholic Church since the beginning, as evident in the writings of the Church Fathers. If you read the Church Fathers you will recognize the Church in their writings. As below, in this excerpt from St. Justin Martyrs First Apology, written in the middle of the second century A. D., his description of the Eucharistic celebration is very familiar to Catholics today, because the rites are essentially the same. What Catholics will also find familiar is his description of our faith in the Real Presence of Christ in the Eucharist.
After we have thus washed the one who has believed and has assented [a reference to one being baptized into the Church], we lead him to where those who are called brethren are gathered, offering prayers in common and heartily for ourselves and for the one who has been illuminated [baptized], and for all others everywhere, so that we may be accounted worthy, now that we have learned the truth, to be found keepers of the commandments, so that we may be saved with an eternal salvation. Having concluded the prayers, we greet one another with a kiss. Then there is brought to the president of the brethren bread and a cup of water and of watered wine; and taking them, he gives praise and glory to the Father of all, through the name of the Son and of the Holy Spirit; and he himself gives thanks at some length in order that these things may be deemed worthy.
When the prayers and the thanksgiving are completed, all the people present call out their assent, saying: “Amen!” Amen in the Hebrew language signifies so be it. After the president has given thanks, and all the people have shouted their assent, those whom we call deacons give to each one present to partake of the Eucharistic bread and wine and water; and to those who are absent they carry away a portion.
We all this food Eucharist; and no one else is permitted to partake of it, except one who believes our teaching to be true and who has been washed in the washing which is for the remission of sins and for regeneration, and is thereby living as Christ has enjoined. For not as common bread nor common drink do we receive both flesh and blood for our salvation, so too, as we have been taught, the food which has been made into the Eucharist by the Eucharistic prayer set down by Him, and by the change of which our blood and flesh is nourished, is both the flesh and the blood of that incarnated Jesus.
The Apostles, in the Memoirs which they produced, which are called Gospels, have thus passed on that which was enjoined upon them: that Jesus took bread and, having given thanks, said, “Do this in remembrance of Me; this is My Body.” And He imparted this to them only.
First Apology, by St. Justin Martyr (inter AD 148-155), from The Faith of the Early Fathers, Vol. 1 by William A. Jurgens, Liturgical Press, Collegeville, MN, 1970.
Be Christ for all. Bring Christ to all. See Christ in all.