Most people assume that they know what the word “Catholic” means, but in fact, it means several different things. Some of the more common meanings are:
1. “Not Protestant.” The Anglophone world has been dominated by Protestant varieties of Christianity for almost half a millennium, and for much of that time “Catholic” has been used as a denominational label, on a par with “Lutheran” and “Baptist.” Of course, there are many Christians who are neither Protestant nor Catholic (I’m not thinking of Anglican proponents of a via media here, but rather thinking of Greek and Russian Orthodox, as well as Arab, Syrian, Coptic, and Assyrian branches of Christianity).
2. “Christians who like sacraments, candles, high liturgy with colorful vestments, incense, praying to saints, ecclesiastical hierarchy, and medieval theologians.” The advantage of this definition is that it is at least positive instead of simply a rejection of Protestantism. This is the meaning of “Catholic” in the phrase “Anglo-Catholic,” which refers to Anglicans with a fondness for “smells & bells.” But again, many of these elements (with a different selection of medieval theologians) would characterize varieties of Eastern Christianity.
3. “Part of the Christian denomination presided over by the Roman Pope.” This excludes both Anglo-Catholics and sede vacantists, the latter being traditionalist Roman Catholics who feel that the recent popes have deviated from traditional Catholic teaching and therefore are not valid popes. (The name comes from the Latin sede vacante, meaning “while the [papal] throne is vacant.”) Although a narrower definition than the preceding two, it is not necessarily that much more precise, as there are a variety of ways to define membership in the Roman Catholic Church. The church hierarchy itself reports membership numbers which include all those baptized into the denomination, regardless of whether they still attend mass or profess to believe any aspect of doctrine, although some rigorists would exclude such nominal Catholics from their definition.
4. “The true Christian Church founded by Christ, present wherever true Christians are.” This sense of “Catholic” opposes it to “schismatic,” people in a particular locale or region who break away from all Christians elsewhere. This is the sense in which Augustine used the term in his writings in the 4th and 5th centuries (he certainly didn’t use the term to mean “non-Protestant”!), and is the sense in which Protestants and Orthodox as well as Catholics recite the Nicene Creed’s confession of “one holy, catholic, and apostolic Church.” It would be strange indeed for non-Roman Catholics to recite a creed saying, “I believe there is one true Church over there, and I am not part of it.”
5. In the phrases “Catholic truth” or “Catholic teaching,” it refers to teaching that is universally held among Christians, as opposed to distinctive beliefs of Christians in one area or one group. Vincent of Lérins offered what has become the most widely accepted definition of “Catholic” in this sense: “What is believed everywhere, always, and by all.” Of course, universals always require a scope, which Vincent does not make explicit, but “everywhere” and “always” should of course be taken to mean wherever and whenever there were Christians. “By all” is trickier, because Vincent would presumably not have included heretics such as gnostics or schismatics such as Novatianists in his category of “all,” but if one narrows the category too much then “by all” becomes tautological: any belief is believed by all who believe it.
The contentious question, then, is what these different senses of the term “Catholic” refer to. Basically everyone agrees that senses #1 and #2 are larger than #3 (this is empirically verifiable). Between the Council of Trent (the Roman papacy’s answer to the Protestant Reformation) and the First Vatican Council (1868-1870), the Roman Catholic party line was that senses #3-5 simply refer to the same group of people. They interpreted the patristic doctrine extra ecclesia nulla salus (“outside of the Church no one is saved”) as referring to the Roman Catholic Church specifically, in keeping with the teaching of Pope Boniface VIII (d. 1303) in his bull Unam Sanctam that submission to the Pope was absolutely necessary for salvation. On this view, all true Christians were within the Roman Catholic Church (although the converse did not hold: those within the Roman Catholic Church were not necessarily true Christians), and “Catholic truth” was that body of doctrine taught by “all” the bishops of the Roman Catholic Church, i.e. the magisterium. Protestants were ipso facto condemned.
Meanwhile Protestants took a few different lines. Protestant theologians all (or almost all) asserted that they were part of the “one, holy, catholic, and apostolic Church,” which required explaining “catholic” differently than loyalty to the pope. Since the papacy rejected almost all of the reforms proposed by Protestants, many Protestants viewed senses #3 and #4 above as mutually exclusive, although some followed Luther in allowing for a little overlap. The lack of a unified anti-papal organization distinguished the notion of a “Catholic Church” in this sense from an institutional unity, so that shared doctrine as indicated in sense #5 became more important as a definition of Christian unity and the key to recognizing good Christians who belong to other denominations.
Eastern Orthodox (and Oriental Orthodox and the Church of the East) had long earlier concluded that submission to the Roman pope was not the defining character of the Church of Christ, and they too continue to confess into their creed that they are part of the Catholic Church. There are different self-governing ecclesiastical hierarchies among both the Eastern Orthodox (Greek, Russian, Bulgarian, Serbian, Rum Orthodox, Georgian, etc.) and Oriental Orthodox (Armenian, Syrian, Coptic, Ethiopic), so they too concluded that one or another hierarchy was not as important as orthodox doctrine and sacramental unity (shared communion), although they do emphasize the visible unity of the church and the apostolic succession of the bishops to a greater degree than Protestants. It is obvious to anyone who knows Greek that the term “catholic” comes from καθ’ ὅλην ἐκκλήσιαν (“according to the whole church”) or ἡ καθ’ ὅλην γῆν ἐκκλήσια (“the church in all the land”), and makes no mention of the pope or hierarchy; “catholic doctrine” in sense #5 was understood to refer to “ecumenical councils,” that is, councils which (at least notionally) involved the entirety of the Church and whose decisions were accepted by the Church.
With the modern ecumenical movement, many Protestants dropped the requirement of shared doctrine from their definition of the Catholic (i.e. universal) Church, and have recognized other Christians with whom they have larger theological disagreements. On this model, sense #3 of “Catholic” describes a part of the group indicated by sense #4. On the other hand, the Roman Catholic Church at Vatican II adopted as dogma the negation of Pope Boniface VIII’s requirement: it is not absolutely necessary for salvation to be in submission to the Roman pontiff. (This has caused conservative Catholic sources I have looked at to resolve the tension by arguing one of the following: (1) Unam Sanctam does not in fact fulfill the requirements of the Vatican I definition of papal infallibility, (2) Unam Sanctam does not mean that it is absolutely necessary for salvation to be in submission to the Roman pope, or (3) Vatican II and subsequent popes are apostates and not true Catholics). Instead, Christians and even non-Christians of good will can be saved. The doctrine extra ecclesia nulla salus has been reinterpreted to mean that all who are saved are in some sense (without knowing it) spiritually connected to and dependent upon the Roman Catholic Church, even if they reject and repudiate the Roman Catholic Church they know (although perhaps they can’t be virtuous enough for salvation if they reject it too vociferously). On this view, the Roman Catholic Church (sense #3 of “Catholic”) is still the one and only universal Church (sense #4 of “Catholic”), but now both definitions have significant footnotes: the Roman Catholic Church is held to have this non-visible wing of people who are evidently outside of it but mystically inside of it, and some of them are probably Christians of other denominations (which are not therefore, as denominations, other churches or other parts of the sense #4 “Catholic” Church). Sense #5 is still understood to be the teaching of the Roman Magisterium, although it is progressively more difficult to interpret all the various teachings throughout the ages consistently, and so some, such as Pope Boniface VIII’s Unam Sanctam, get quietly neglected.
“Ecumenical” is still a dirty word among many Eastern and Oriental Orthodox Christians, although their participation in the World Council of Churches has helped them see commonalities across Christological divisions.
Is the Roman Catholic Church the Catholic Church? Is the Pope Catholic? Depending upon whom you ask, the answers will vary. But in light of varying meanings of the term “Catholic,” it is important in our ecumenical discussions not to equivocate, but to distinguish the different senses of the term, even for those of us who believe there is a common referent.