Why can’t a Catholic take communion in a Protestant church? If I am at a wedding for example, it just seems like a neighborly thing to do.
Neighborliness is indeed a virtue, and it’s good to want to find common ground with our separated brethren. But some things cannot be compromised for society. This is one of them. Remember that communion was the first dividing controversy in Jesus’ ministry. The Eucharist as Catholics believe it has always been a source of division in the world—as is Jesus.
For the first 1500 years of the Church there was one understanding of what the Eucharist is. Read the Church Fathers and you will see: though they did not have the term “transubstantiation.” They believed that Christ is really and truly present in the Eucharist and they took great pains to keep those who did not believe or were in a state of sin from receiving it.
50 years after the reformation, a book was published: 200 Views of the Eucharist. What Protestants do and what we do are two very different things and should not be confused.
The short answer to your question is that intercommunion with Protestants is forbidden both by the Catechism (CCC1400) and the Canon law (Canon 844).
Canon 844 states as follows: “Catholic ministers may licitly administer the sacraments to Catholic members of the Christian faithful only and, likewise, the latter may licitly receive the sacraments only from Catholic ministers. Whenever necessity requires or a genuine spiritual advantage commends it, and provided the danger of error or indifferentism is avoided, Christ’s faithful for whom it is physically or morally impossible to approach a Catholic minister, may lawfully receive the sacraments of penance, the Eucharist and anointing of the sick from non-Catholic ministers in whose Churches these sacraments are valid.”
Now, let’s look a little deeper:
(1) The Protestant churches are not churches under Catholic thinking. Christ established ONE church that subsists in its fullness in the Catholic faith. The Catholic Church views these other churches (Presbyterian. Lutheran, Episcopal, non-denominational) not as churches but as ecclesial bodies of believers that do not have the fullness of the faith. Most importantly, they do not have sacraments, apart form marriage and baptism, because they do not have a valid priesthood. Hence, their communion is, for Catholics, invalid as well as illicit (it isn’t what it is supposed to be and it is forbidden for Catholics to receive it). Let me repeat: there is no Real Presence. Catholics may not participate by receiving communion. To do so knowing full well that the Church forbids it may constitute a grave (mortal) sin, that of blasphemy.
(2) The Church teaches you can be in communion with only one body at a time. If you are in communion with the Catholic Church, then you cannot be in communion with another ecclesial body. Remember that as a Catholic you are “married” to Jesus through His Church and one of the sacraments of that marriage is the Eucharist. Taking communion in another Church is like cheating on your spouse.
(3) When you accept communion you are saying I believe (that’s what the Amen! Is, after all) to all that that particular body is teaching–that’s what communion is. If you care Catholic you do not (or should not) believe what these other ecclesial bodies believe about Holy Communion and so you should not receive communion there, no matter what well meaning Protestants say. A Catholic looks to the Catholic Church to teach him, form his conscience and guide his life. Protestants view things very differently from Catholic and although their advice (“It’s Jesus’ table, you are welcome! It’s wrong of your church to say you can’t come.”) may be well meaning, it is not the advice of the Church. They may be willing to have you, but you are not free to participate. And even if they claim to believe in the Real Presence, they do not have a valid priesthood (not even the Episcopalians) and that is a requirement for a valid Eucharist. ONLY the Catholic, some Old Catholic, and Orthodox Churches have a valid and sacramental Eucharist.
(4) When you receive communion in another ecclesial setting, you cause scandal. As much as we wish for Christian unity, we do not have it and making it appear that we do sends as signal to those with weak faith or unformed faith that it doesn’t matter where one worships. Do you really believe that? Is receiving a cracker and some grape juice (or even bread and wine) the same as receiving Our Lord, Body and Blood, Soul and Divinity?
The Eucharist is the source, summit and focus of our life in Christ, it communicates Christ to us and is a real and powerful means of grace. It should not be confused with the communion services of other traditions. When you participate in a Protestant communion, not believing what they believe, but making an outward show that you do, you are giving at least outward honor that should go to God to the mere creatures of bread and wine. Given that God in the person of Jesus established communion in the Church (remember the Last Supper?) and told us what it is and means (remember the Bread of Life discourse, which ends with John 6:54. Look it up…) we owe it to God to participate in that sacrament as, and only as, He sets out. And he sets that out through the Church to whom the sacrament was given. That way is not a Protestant communion service, it is the Catholic mass.
(5) The Episcopal ecclesial bodies (there are now many schisms within that body) pose a particular problem because the liturgy looks so much like ours, and many of them will argue that they, too, believe in the Real Presence. In fact, some of the more orthodox Episcopal congregations are much more reverent towards their communion than Catholics are towards the Eucharist.
There are a couple of problems here: First, regardless of what latter day Episcopalians might think, the schismatics who broke away from the Catholic Church and formed the Anglican Communion did not intend their communion as a Real Presence. (You can see this reflected in Article 28 of the The 39 Articles; for what it is worth, Article 22 rejects Purgatory and Article 25 rejects all the sacraments except baptism and holy communion–with the net result that matrimony is not a sacrament under the 39 articles either.)
Further, the Church has ruled very clearly that holy orders in the Episcopal ecclesial bodies are not valid. So: No priesthood, no valid Eucharist, no discussion, not matter how much it resembles Catholic worship on the surface and no matter how much Episcopalians argue to the contrary. For Catholics the matter was settled by the declaration of Pope Leo XIII in Apostolicae Curae.
(6) Canon 844 does provide for exceptions but only for those churches with a valid priesthood and in cases of necessity. “Being neighborly” at a Protestant wedding doesn’t constitute necessity and Protestants do not have a valid priesthood.
We are called as Catholics to witness to our faith. That means living visibly as Catholics, showing the world the incredible grace that flows through Christ’s Church. Among those graces is the incredible privilege of receiving Jesus Christ, body and blood, soul and divinity, at mass. It is sometimes good in the interests of friendship and ecumenism to attend Protestant services with our loved ones. But what a witness it would be to refrain from communion and explain, gently and lovingly, why!
And I hope your answer isn’t “because the mean old Church tells me I can’t.” The Church, like a good mother knows her children need guidance. Smart children accept that. And it is worth remembering that if we do as the Church teaches (not as this, that or the other priest, deacon, layman or apologist interprets it), she will NEVER lead us away from God.
If this still doesn’t make sense to you, try this: give the assent of faith. Tell God you are having trouble understanding this, and ask His assistance in coming to a deeper appreciation of the Eucharist and these teachings of the Church. Promise Him (and yourself) you will trust the Church in this matter and you will neither speak to anyone against Church teaching in this matter, nor act against it. With the assent of faith eventually comes understanding. As Christians, assent comes first: we believe so that we may understand. If it’s the other way around—understanding before believing—it isn’t really faith, is it? And isn’t it just a little prideful to decide that we know better than 2000 years of Church teaching?
As for being neighborly: we have the fullness of the faith. We have Jesus truly and substantially present at every mass, and we receive Him into our very selves. Just stop for a moment and think about the incredible beauty of that. We have the fullness of sacraments as channels to the grace we need in everyday life to help us on our journey to heaven. Isn’t the neighborly thing to do to invite others to come, share the feast with us rather than the other way around?