“The Church, no doubt, has always kept, and wishes still to maintain everywhere, the language of her Liturgy; and, before the sad and violent changes of the sixteenth century, this eloquent and effective symbol of unity of faith and communion of the faithful was, as you know, cherished in England not less than elsewhere. But this has never been regarded by the Holy See as incompatible with the use of popular hymns in the language of each country. Such hymns, moreover, are useful to familiarize the people with the great truths of faith, and to keep alive their devotion.”
— LEO XIII, POPE (8 June 1898)