My friend David Schütz (please visit and profit from his inestimable blog) often speaks of the Una Sancta - that is, the One Holy Catholic Church that we confess in the Apostles' Creed:
Credo in Spiritum sanctum, sanctam Ecclesiam catholicam, sanctorum communionem, remissionem peccatorum...
What does this imply? That we believe in the equal Deity of the Holy Ghost, Who is the Soul of the Church, Who makes holy the saints, Who effects the consecration of the Holy Mysteries, Who is Himself the Remission of sins. That we acknowledge the ekklesia, literally the calling together, the convocation, of all those translated by God out of the power of darkness into the kingdom of Christ (cf. Col. i, 13) - which is at once the fellowship (koinonia) of the saints, that we may share their lot in light (cf. Col. i, 12), those made and called to be holy in this new kingdom of Christ, and - since the Eucharist makes the Church - the sharing of holy things, above all of the Holy Gifts of the Divine Eucharist, which sanctify and purify and deify us, remitting sins by burning them away in the fire of love, and obtaining of God all graces by their mystical oblation in the Sacrifice of the Mass, since these Holies we partake of are Christ and His Redemption wrought for us made present - redemption, the forgiveness of sins (cf. Col. i, 14); and to which access - to the Church, to the communion of Saints, to Holy Communion - may alone be gained by baptism, the remission of sins, and which can be regained if by our sins our share in holiness is lost through the sacrament of penance, the 'second baptism', the remission of sins.
Why this sudden thought?
Because to-day (now almost past; after spiritually a rather bad day in which I'd started Matins in the morning, split it up due to its length, and only finished it with Te Deum after 4pm, I've just finished the Office, by reading Lauds, Prime, Terce, Sext, None, Vespers and Compline all at once) is the feast of two very pillars of the One Holy Church: the blessed Apostles Simon and Jude - and because of the Anglican collect therefor, which is a very decent prayer. I happen to know that this feast and this collect are respectively the feast-day and the official prayer of the Prayer Book Society of Australia, and I take this opportunity to pray for our separated brethren, "that they may all be one" (St John xvii, 21f) with us, in Holy Church united, that the world may know Jesus Christ and God His Father and their love (their Love, the Holy Ghost, the uncreated Gift that divinizes) for all to be gathered into one (cf. St John xvii, 23):
O Almighty God, who hast built thy Church upon the foundation of the Apostles and Prophets, Jesus Christ himself being the head corner-stone (cf. Eph. ii, 20); Grant us so to be joined together (cf. Eph. ii, 21) in unity of spirit (cf. I Peter iii, 8; Eph. iv, 3) by their doctrine, that we may be made an holy temple (cf. Eph. ii, 21) acceptable unto thee (cf. I Peter ii, 5); through Jesus Christ our Lord. Amen.