Our Understanding of Other Christians
The Catholic Church does not take a simplistic view of other Christian communities. Her understanding of the various communities is well-nuanced and therefore does not lump them all together.

The Orthodox Churches are seen as “true churches”. The Catholic Church recognises the Orthodox churches as true churches; in fact, they are frequently called “sister” churches. These churches born in the East, although not in communion with the Bishop of Rome, are distinctly characterised by apostolic succession and therefore have valid sacraments.

We do estimate that such churches are suffering from a “wound” since they do not recognise the primacy of the Bishop of Rome, the Pope, among other Patriarchs. However, the wound is not so severe that it has caused them to lose the gravity of the marks of a true Church: oneness, holiness, catholicity and apostolicity. They still contain sufficient marks to constitute true churches.

[Note: Of course, there are some Eastern Churches who have throughout the centuries returned to full communion with the Bishop of Rome and have come to be called “Eastern Catholic Churches”. These are not wounded and continue to exercise their ecclesial life based on the distinctives of their traditions in consistency with the deposit of faith and in full communion with the Pope. There are also about two Eastern Churches which have never broken communion with Rome before in the course of their history.]

Protestant communities are called “ecclesial communities”. Whilst there is a measure of woundedness in the Eastern Churches, it said that the “wound is still more profound” in the Protestant denominations. The wound is so profound that these communities do not sufficiently possess enough marks of a church to be properly called “churches”. Therefore, the Catholic Church calls these communities “ecclesial communities originating from the Reformation”, a term used to refer to Protestants and Anglicans (the latter often do not identify themselves as “Protestants”, therefore it is right to identify them separately with due respect to their self-identity). A document of the Catholic Church says, “Despite the fact that this teaching has created no little distress ... it is nevertheless difficult to see how the title of 'Church' could possibly be attributed to them”.

The Catholic Church does not mean these terms to be derogatory; rather, they are meant to be honest terms. She would expect no less from her dialogue partners. In the same way, there are well-meaning Protestant segments who call the Catholic Church “the Harlot of Babylon” and the Pope “the antichrist”. The Catholic Church does not react even to such derogatory name-calling, perhaps by way of respecting the rights of such well-meaning Christians to determine what they truly believe and to be honest about it. A Pentecostal theologian once said in a dialogue with the Catholic Church, “We think you Catholics are not saved, and our aim is to save you!” The point was well-received because the open honesty was respected.

But at the same time, the Catholic Church continues to recognise that within these ecclesial communities is to be found elements of truth and sanctification which assist people in the salvific process. The Catholic Church also continues to acknowledge, admire and deeply respect those who continue to proclaim Christ in local and foreign lands, the evangelists and those who die because of their faith.

And yet, whilst the Second Vatican Council's opening to other faiths recognised that there were “many elements of sanctification and truth” in other Christian denominations, the Church stresses that only Catholicism has all the elements to be Christ's Church fully.

It is possible, according to Catholic doctrine, to affirm correctly that the Church of Christ is present and operative in the churches and ecclesial communities not yet fully in communion with the Catholic Church, on account of the elements of sanctification and truth that are present in them […] In fact the Spirit of Christ has not refrained from using them (other Christian denominations) as instruments of salvation, whose value derives from that fullness of grace and of truth which has been entrusted to the Catholic Church.”

[Responses to Some Questions Regarding
Certain Aspects of the Doctrine of the Church]

Recognising also that the Protestant Reformation took place in waves, and that each wave of the Reformation represented a further drift away from the fullness of the deposit of faith, the Catholic Church further categorises the ecclesial communities into three separate clusters. The first batch of communities arising from the Reformation is known as the “Reformation communities” (i.e. Reformed, Anglican, Presbyterian, Lutheran). The second batch, most often further breakaways from the Reformation communities themselves, are termed “free communities” (i.e. Methodists, Baptists, Quakers). Finally, the subsequent communities arising from further breakaways are categorised under “sects” (i.e. Brethren, Salvation Army, Pentecostal denominations, Seventh Day Adventists, etc).