What is the counterpart to the Uniate Churches? It might seem simplest to conceive this as the Roman Church, meaning all Catholics who use the Roman rite. That is, at any rate, an intelligible and reasonable use of the term "Roman Catholic." A Roman Catholic is a Catholic who uses the Roman rite, just as an Armenian Catholic is one who uses the Armenian rite. It would then seem obvious to call all Catholics who do not use the Roman rite Uniates. As far as liturgy goes, there is nothing to say against such a classification. In this sense the faithful of Milan and the Mozarabic families in Spain are Uniates. Their rite is not Roman; except for later Romanizing their rites have no more in common with that of the Roman mother-Church than have those of Eastern Catholics. So, also, the old Gallican Catholics, the people before the time of Charles the Great, who used the Gallican rite, were Uniates. But in this case we need not trouble much about them, since, except for its relics at Milan and Toledo, the Gallican rite disappeared long before anyone thought of the word Uniate as a special name.
Yet this is not common use. A Catholic of Milan knows quite well that he is Ambrosian in rite, but he would never think of calling himself a Uniate. He would probably, though foolishly, resent being put in the same category as the Eastern people. Practically in this classification all Western Catholics, all who use Latin as their liturgical language, are put in one class, Eastern Catholics in the other.
Language used in the liturgy is almost the worst possible basis of distinction; yet in this case it comes practically to that. The reason is that liturgy is not really the only, nor even the essential, basis of this distinction. We shall get it better by thinking of the old Patriarchates, which are the reason of the present distinction of rites among Catholics.
Once there were three Patriarchates in all Christendom, those of Rome, Alexandria, Antioch. Now Catholic Canon Law recognises five: Rome, Constantinople, Alexandria, Antioch, Jerusalem. Putting the Roman Patriarchate on one side, we call a member of any of the other four a Uniate. So, since the faithful of Milan and Toledo belong to the Roman Patriarchate, we shall not call them Uniates. We arrive, instead, at the distinction between, not Romans (in the sense of rite), but Latins and Uniates. Latins include Ambrosians and Mozarabs, as well as the vast majority who have the Roman rite in any language. Uniates are Catholics of the old
