But since the Modernists (as they are commonly and rightly called) employ a very clever artifice, namely, to present their doctrines without order and systematic arrangement into one whole, scattered and disjointed one from another, so as to appear to be in doubt and uncertainty, while they are in reality firm and steadfast, it will be of advantage, Venerable Brethren, to bring their teachings together here into one group, and to point out the connexion between them, and thus to pass to an examination of the sources of the errors, and to prescribe remedies for averting the evil.
Pope Pius XThe Church alone, being the Bride of Christ and having all things in common with her Divine Spouse, is the depository of the truth.
Pope Pius XIs 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 X