Can non-Catholic Christians receive communion in the Catholic Church?
Catholic Answers Senior Apologist Jimmy Akin explains why non-Catholics can only receive the Eucharist under very limited extra-ordinary circumstances.
Jimmy Akin was born in Texas and grew up nominally Protestant. At age 20 he experienced a profound conversion to Christ. Planning on becoming a Protestant pastor or seminary professor, Jimmy started an intensive study of the Bible, but the more he immersed himself in Scripture, the more he found...
"The gravest obligation requires the acceptance and practice, not of the religion which one may choose, but of that which God prescribes and which is known by certain and indubitable marks to be the only true one."
~ Leo XIII in his Encyclical Immortale Dei (November 1, 1885); on our fundamenal duty; (from the article Religious Toleration)