It has expressed this distinction in documents such as Unitatis redintegratio, the Second Vatican Council's decree on ecumenism, which states: "quite large communities came to be separated from full communion with the Catholic Church.
[6] Nonetheless, the Second Vatican Council used the word "communion" in a sense other than communio in sacris when speaking of Christians separated from the Catholic Church.
The Catechism of the Catholic Church, citing the Second Vatican Council and Pope Paul VI, states:[7] "The Church knows that she is joined in many ways to the baptized who are honoured by the name of Christian, but do not profess the Catholic faith in its entirety or have not preserved unity or communion under the successor of Peter" (Lumen gentium 15).
Those "who believe in Christ and have been properly baptized are put in a certain, although imperfect, communion with the Catholic Church" (Unitatis redintegratio 3).
[11] The autonomous Catholic churches in full communion with the Holy See are: Jus novum (c. 1140-1563) Jus novissimum (c. 1563-1918) Jus codicis (1918-present) Other Sacraments Sacramentals Sacred places Sacred times Supra-diocesan/eparchal structures Particular churches Juridic persons Philosophy, theology, and fundamental theory of Catholic canon law Clerics Office Juridic and physical persons Associations of the faithful Pars dynamica (trial procedure) Canonization Election of the Roman Pontiff Academic degrees Journals and Professional Societies Faculties of canon law Canonists Institute of consecrated life Society of apostolic life As a practical matter for most Catholics, full communion means that a member of one Church may partake of the Eucharist celebrated in another,[12] and for priests, that they are accepted as celebrants of the Eucharist in the other Church.
Restrictions in this matter were already in force in the second century as witnessed to by Justin Martyr in his First Apology: "No one is allowed to partake (of the Eucharist) but the man who believes that the things which we teach are true, and who has been washed with the washing that is for the remission of sins, and unto regeneration, and who is so living as Christ has enjoined.
[12][14] Being "in full communion with the Catholic Church" requires that they "firmly accept" its teaching on faith and morals.
[21] Eastern Orthodox have an understanding of what full communion means that is very similar to that of the Catholic Church.
[22] Though they have no figure corresponding to that of the Roman Catholic Pope, performing a function like that of the Pope's Petrine Office for the whole of their respective communions, they see each of their autocephalous churches as embodiments of, respectively, the One, Holy, Catholic and Apostolic Church.
They too consider full communion an essential condition for common sharing in the Eucharist.
The Chaldean Catholic Church shares a similar history with both, but is currently in full communion with neither.
It applies the first term to situations "where between two Churches, not of the same denominational or confessional family, there is unrestricted communio in sacris including mutual recognition and acceptance of ministries", and the second term to situations "where varying degrees of relation other than full communion are established by agreement between two such Churches".
[36] Churches or denominations holding to open communion allow all persons who consider themselves "Christian believers" to participate, even without any arrangement of full communion with the other church or denomination involved, and still less requiring an arrangement involving interchangeability of ordained ministers.