"In one Holy Catholic Church," on which, though one might say many things, we will speak but briefly.  It is called Catholic then because it extends over all the world, from one end of the earth to the other; and because it teaches universally and completely one and all the doctrines which ought to come to men's knowledge, concerning things both visible and invisible, heavenly and earthly;...for this cause the Faith has securely delivered to you now the Article, "And in one Holy Catholic Church;" that you may avoid their wretched meetings, and ever abide with the Holy Church Catholic in which you were regenerated. And if ever you are sojourning in cities, inquire not simply where the Lord's House is (for the other sects of the profane also attempt to call their own dens houses of the Lord), nor merely where the Church is, but where is the Catholic Church. For this is the peculiar name of this Holy Church, the mother of us all, which is the spouse of our Lord Jesus Christ, the Only-begotten Son of God.”

--Cyril of Jerusalem, Catechetical Lectures, 18:25, 23, & 26 (A.D. 350)