Is it permitted for Catholics to be present at, or to take part in, conventions, gatherings, meetings, or societies of non-Catholics which aim to associate together under a single agreement everyone who, in any way, lays claim to the name of Christian? In the negative! ... It is clear, therefore, why this Apostolic See has never allowed its subjects to take part in the assemblies of non-Catholics. There is one way in which the unity of Christians may be fostered, and that is by furthering the return to the one true Church of Christ for those who are separated from Her.
Pope Pius XThe organic constitution of the Church is not immutable; but Christian society, just as human society, is subject to perpetual evolution.
Pope Pius XIt is impossible to approve in Catholic publications of a style inspired by unsound novelty which seems to deride the piety of the faithful and dwells on the introduction of a new order of Christian life, on new directions of the Church, on new aspirations of the modern soul, on a new vocation of the clergy, on a new Christian civilisation.
Pope Pius XThe proposition that the principal articles of the Apostles' Creed did not have the same meaning for the Christians of the earliest times as they have for Christians of our time is hereby condemned and proscribed as erroneous.
Pope Pius XWhat will it cost you, oh Mary, to hear our prayer? What will it cost you to save us? Has not Jesus placed in your hands all the treasures of His grace and mercy? You sit crowned Queen at the right hand of your son: your dominion reaches as far as the heavens and to you are subject the earth and all creatures dwelling thereon. Your dominion reaches even down into the abyss of hell, and you alone, oh Mary, save us from the hands of Satan.
Pope Pius X