Ever since my son and his fiancee got engaged, I've been pondering how to explain to my non-Catholic relatives why they will not be invited to receive Communion at the wedding mass. This is the result of much reflection, and although it may not make those relatives happy, it is hoped to shed some light.
Catholics and other Christians have been in disagreement ever since the split in the church about what it is they are actually receiving. This is the heart and core of the difference between denominations. There are many other disagreements, but none as key to the problems that have caused the scandalous division between Christians. I won't address the other issues, but do hope this explains why we, as Catholics, don't share.
Having been raised a Presbyterian, I went through Communicants Class to prepare for full entry into the Presbyterian Church and to begin receiving communion. In this class it was emphasized that communion services reenact the Last Supper and that the bread and grape juice we would receive are just symbols from that first communion service. I still believe this is true. Presbyterians and other protestants serve a symbol for the body and blood of Jesus Christ. They themselves believe that is what they are doing and they are absolutely correct. I respect their desire to participate in the Last Supper using these symbols.
Catholics do not receive a symbol. They receive the real thing. The high point of Mass, the consecration, is a miracle. The host and cup are lifted up by the priest, and at that point, although they retain the appearance of bread and wine, transubstantiation takes place--they become the actual body and blood of Jesus Christ. The host and cup are the presence of the Lord, and are treated with the greatest reverence possible. There are saints in the Catholic Church who have willingly and lovingly sacrificed their lives to protect consecrated hosts. Because this is the faith of the Catholic Church, no one, not even Catholics are allowed to receive communion without extensive education to prepare for this great privilege. Even if a non-Catholic professes belief in this miracle, they are not invited to partake until they have been adequately prepared--and this usually requires entry into the Catholic Church. And Catholics who usually receive communion are expected to not participate if they are not in a state of grace--if they have committed a serious sin they need to go to confession before they receive communion again. You don't handle pure objects with soiled hands.
Throughout history, the greatest insult a non-Catholic can do to a Catholic is to desecrate a consecrated host. Sadly, at this point in history, this offense is taking place regularly. People hostile to the Catholic Church know they can get attention by calling the host a "cookie" and are doing vile things to them whenever they can get their hands on them. Clearly this is a hate crime, but I have yet to hear a non-Catholic call it so.
Non-Catholics are sometimes puzzled at actions or gestures customary with Catholics. Genuflection is one. Why do we do it? Because after communion, any leftover consecrated hosts are put in the tabernacle--a place of high honor for Christ, flanked always with lit candles. The lit candle is a sign to others that Christ is present in the church specifically in the consecrated host. We bend our knees to show respect--the same respect others would show to their king, we show to The King. When you enter or leave the throne room of the king, protocol requires a gesture. Genuflection is ours. The church is the throne room of the king, the tabernacle is the throne. We face the tabernacle when we genuflect. If there is no consecrated host, the candles are not lit and the tabernacle is left open. There is no need to genuflect.
When you understand what we are receiving, the gestures and postures we assume suddenly make sense. It should also make sense that if you have no faith that transubstantiation takes place--if you do not believe that the host is our most holy possession of all--you should not touch it. When you are invited into someone's home, you respect their property. You don't jump on their furniture, deliberately scratch their tables, or smash their lamps. You have been taught not to do this. To receive communion without teaching is like jumping on someone's best furniture. You do not know what you are doing!
There is yet one more reason for non-Catholics not receiving Catholic communion. All who receive it are showing a sign of unity with each other--a common faith. Since all Christians do not believe the same thing about communion, it would be hypocrisy to share communion when not in agreement about this core practice. That is why non-Catholics will be invited at the wedding to pray for unity during communion. Rather than enacting a false sign of unity when there is none, we ask you to join us in unity by praying for understanding and a softening of hearts towards unity. This is also one of two reasons why Catholics do not participate in communion in other denominations, even when invited. It would be pretending that we are in more agreement than we actually are. It would not be true. And it would be doubly hypocritical to pretend unity using the most sacred sacrament we have been given.
The second reason why Catholics do not participate in non-Catholic communion services may make some of you angry. I'm sorry about that, but I can't think of a way to soften the reason. Here it is. If you are hungry and need something to eat, and one person offers you bread, while another person offers you a picture of bread, which one are you going to eat with? Communion is spiritual food. Once you have received the real thing, the symbol will not satisfy that spiritual hunger. Furthermore, you have a sense of dishonoring the real thing by accepting the symbol.
One final comment, and then I'm done. Going back to when I was in Communicant's class. It was emphasized in the class that the bread and grape juice were just symbols. That was what I was taught. But when the time came, and the cube of bread and cup of juice was offered to me, I said a little prayer. It was this. "I know they told me that this is just a symbol, but I want it to be the real thing." I did not know anyone had the real thing. Imagine my astonishment when I found out that Catholics could give me what I was hungering for. From the moment I learned that, there was no turning back. This is why I am Catholic, and this is why I agree with the Catholic Church, that we should not share with those who don't believe in the real presence of Christ in communion.