Those words are part of the Creed, but both Catholics and (some) Protestants speak them and profess them to be true. They are called the four marks of the Church. So what do they mean then to each group?
That is the question that Bryan Cross just posted about on his blog, and he answered it much better than I could have!
Excerpt (on the Holy mark):
Sanctum:
The Catholic understanding of the holiness of the Church is that the Church is actually holy. This does not mean that her members on earth have perfect holiness, or that they all have the same degree of holiness, or even that the majority are exceptionally holy; in fact we are all still sinners. Nor does it mean that in their good deeds pagans and heretics can never outshine Catholics. But it does mean that the Church stands apart from the world in her godly practice and sanctification; she testifies by the manner of her life and witness to the righteousness of God, the dignity of human life, the goodness of creation, the future judgment and the life of the world to come. Her members on earth have a “real though imperfect” holiness (CCC 825), especially insofar as they receive the life of Christ through the means of grace in the sacraments. Moreover, the canonized saints are examples to us of the sanctifying transformative power of the Holy Spirit working in and through the Church. Through the continuous use of the sacraments and prayer, we are truly and actually transformed into virtuous people.The common Reformed conception of holiness by contrast, is formalized and de-materialized. According to this conception, our holiness is essentially something imputed to us, a legal declaration in which Christ’s righteousness is credited to our account, covering us from God’s wrath, but not transforming us into persons to whom God could honestly say, “Well done good and faithful servant.” All our deeds are as filthy rags. So the Church and the believer are treated by God *as if* holy, as if as holy as Christ, but not transformed so as to be actually holy. (I have explained all this in more detail here. To qualify, I’m speaking of the common contemporary Reformed conception of the gospel, not Calvin’s own position.)
I remember one service (when I went to the Southern Baptist Convention community where I was baptized) and the pastor described our holiness in almost these exact words, the key ones being “imputed” or “declared”.
Everyone in the congregation had their bibles open and were taking notes, as is normal, and all of them listened and took that in, but at this time I had begun considering whether the church I was at was the closest to “true Christianity”, and I thought, “how do I know that what he is saying is really true?” because I had learned by this time that “infused” versus “imputed” righteousness was something debated between Catholics and Protestants and was a key difference.
The entire post is well-worth reading; in short, the Reformed (Protestant) understanding of the four marks of the Church is formalized and de-materialized while the Catholic understanding of the marks is sacramental and visible. For example, Catholics claim that there really are successors of the apostles, the Bishops, and that their succession can be really traced through all the beautiful and ugly history of the world and of the Church to Christ himself and the 12 he chose.
