"It is, moreover, our will that Catholics should abstain from certain appellations which have recently been brought into use to distinguish one group of Catholics from another. They are to be avoided not only as ‘profane novelties of words,’ out of harmony with both truth and justice, but also because they give rise to great trouble and confusion among Catholics. Such is the nature of Catholicism that it does not admit of more or less, but must be held as a whole or as a whole rejected: ‘This is the Catholic faith, which unless a man believe faithfully and firmly; he cannot be saved’ (Athanasian Creed). There is no need of adding any qualifying terms to the profession of Catholicism: it is quite enough for each one to proclaim ‘Christian is my name and Catholic my surname,’ only let him endeavour to be in reality what he calls himself."
The encyclical letter Ad beatissimi apostolorum, November 1, 1914