The Church teaches that during the celebration of Mass the bread and the wine truly become the Body and Blood of Christ. It is a distinctive teaching of the Catholic Church, and at the heart of our worship. This became a struggle for me when I entered college, because I couldn’t tell how the elements were any different, and didn’t know how to answer those who challenged this belief. I ended up asking one of the priests at the Newman Center, which was a blessing. Unfortunately these types of questions are sometimes just left to fester without remedy!
The priest suggested two things, which helped me immensely. The first was study. At a basic level, I didn’t really understand what the Church teaches. We do not claim that the sensible elements change (how it looks, tastes, etc). Instead, we believe that the substance changes (what stands beneath the appearance, classically called “accidents”). This answered my first question; it’s not a question of sensible change, but whether the change is merely symbolic.
In my study I examined the scriptural texts, and realized how strongly Jesus states the truth of the substantial change in the Scriptures (eg “For my flesh is true food and my blood is true drink,” from John 6:55). Paul likewise speaks of it in his letters. Elsewhere you can find a fuller explanation, but I just want to say here that the Catholic belief is certainly not unscriptural.
The other aspect of my study was the writings of the early Christians, shortly after the time of Christ. For example, St Justin Martyr writes this (around the year 150 AD):
“And this food is called among us the Eucharist, of which no one is allowed to partake but the man who believes that the things which we teach are true, and who has been washed with the washing that is for the remission of sins, and unto regeneration, and who is so living as Christ has enjoined. For not as common bread and common drink do we receive these; but in like manner as Jesus Christ our Savior, having been made flesh by the Word of God, had both flesh and blood for our salvation, so likewise have we been taught that the food which is blessed by the prayer of His word, and from which our blood and flesh by transmutation are nourished, is the flesh and blood of that Jesus who was made flesh. For the apostles, in the memoirs composed by them, which are called Gospels, have thus delivered unto us what was enjoined upon them; that Jesus took bread, and when He had given thanks, said, This do in remembrance of Me, this is My body; and that, after the same manner, having taken the cup and given thanks, He said, This is My blood; and gave it to them alone.”
In short, I found that the belief in the true change of the elements is the ancient belief. Reducing it to merely a symbolic/figurative change is a development of the last centuries. Just appeals to the recent teaching of the apostles as the source of his belief–a distance of less than 100 years. Either the apostles completely failed to explain the symbolic nature of the Eucharist and the belief became corrupted within the first generation, or Justin is in fact correctly representing their teaching.
In addition to this objective study, the priest recommended a second approach: prayer. As I began to pray more seriously in the presence of the Blessed Sacrament (and to be more attentive in receiving Communion), I experienced the truth of these words personally. Jesus didn’t desire to leave only a symbolic or figurative presence with us. He is present, truly, under the appearance of the bread and wine.
From that point, instead of experiencing this teaching as a source of confusion, I found it to be a source of Communion—from the Mass I experience today, back through the ages and saints, to Christ Himself.