Now I'm really confused. I'm Catholic. My 15-year-old daughter sometimes goes to her best friend's Lutheran church (the friend also goes to ours occasionally) and takes Communion because the pastor invites all baptized Christians to do so. But I read on Beliefnet that my daughter is wrong to do that. What Catholic doctrine is she going against?
I'm not surprise you're in a muddle. First, the discussion too often switches to the Catholic Church's Katie-bar-the-door policy aimed at preventing non-Catholics from receiving Communion on its turf. There are many exceptions, grave or humorous according to your stance on the issue, whereby outsiders slip through the net and receive contraband sacrament (the writer Michener was allegedly among them), but that's the Roman church's rule, plain and simple.
But you want to know what happens when your daughter, a Catholic, ventures to Communion in a Protestant church. What rule has she violated? In my view, she has violated none. There is no exact teaching.
Catholicism--at least its lawgivers--contend that valid Communion takes place only under its auspices and requires full agreement with the doctrines of the church. Without this "full communion" with what it regards as the only actually true church (see the latest pronouncement), the real thing doesn't happen.
That, of course, is open to debate, even among Catholic theologians. Sacraments are moments of grace. If Protestants observe Communion, can that be an evil whereby the Catholic is put in grave danger? Nobody says that. Could Protestant versions of it lack the 'real stuff'? Sure, but even in that case, wouldn't they simply be ineffective, like a vaccination that for some reason didn't take?
The origin of Communion is, of course, the Last Supper, in which Jesus offered his body and blood for his disciples and for the whole world. Can we truly suppose that the disciples, who were constantly losing track of their mission and purpose, were of one mind and always acted in doctrinal solidarity? One of them, after all, promptly went out and betrayed Jesus.
So who is deserving? There are many answers, none seeming to cover all bases. In the Wesleyan (Methodist) tradition, for example, the gracious outpouring of Communion can convert the seeker in addition to strengthening the believer.
So what your daughter has done fits into a much larger discussion of the origin and purpose of the Eucharist, one that leaves theologians with various interpretations. But she commits no sin, breaks no doctrine. No one says God confines grace to the Roman Catholic Church. It might even slip through in Lutheran Communion.
There may be strong efforts to control the behavior of believers in an effort to stress an awareness of difference--superiority and authenticity--but there is nothing specifically anti-doctrinal about it. An institution's self-interest often collides with matters of faith. On matters of faith, it would seem that your daughter seeks God.
One other matter plays in here. The Second Vatican Council took pains to restore the place of conscience in the lives of Catholics. While conscience must not become an excuse for self-interest or impulse, the Council made clear that it is the final court in helping a Catholic decide what to do--after prayer and due consideration of the church's teachings.