Expert: Edward Bode - 3/13/2009

Question
Are Protestants and Orthodox Christians excluded from Christ's Universal Church on Earth? Or do you think a more ecumenical stance than that is appropriate for Catholics?

Answer
The Second Vatican Council spoke to membership in the Church [founded by Jesus Christ].  The council issued three relevant documents: the Church, Ecumenism, Eastern Churches.  All relate to your questions.  You would do well to read the documents, which should be available in a library
Those documents put the Catholic Church in the forefront of ecumenism.
Since then, the Vatican has established numerous commissions to work with others, including Lutherans, Anglicans, and Orthodox.  Those discussions are still continuing as well as discussions with Muslim and Jewish scholars.
The Catechism of the Catholic Church, which also deals with the same issues, is available online at: usccb.org/catechism/text/index.htm
The relevant passages [beginning at paragraph 811] concern the oneness, the holiness, the catholicity, and the apostolicity of the Church.
Who belongs to the Church comes in paragraphs 836-838. Please read  these paragraphs carefully.  They explain: all are called to the unity of the Church; "fully incorporated" are those in the visible structure of the Catholic Church; those who have faith in Christ and are baptized have an "imperfect" communion with the Church; the Orthodox lack little to attain fulness permitting a common celebration of the Eucharist.
Hope these thoughts help, Mike.  If you wish more, let me know.
Best wishes.