"The only true union"
Also they must restrain that dangerous manner of speaking which generates false opinions and fallacious hopes incapable of realization; for example, to the effect that the teachings of the Encyclicals of the Roman Pontiffs on the return of dissidents to the Church, on the constitution of the Church, on the Mystical Body of Christ, should not be given too much importance seeing that they are not all matters of faith, or, what is worse, that in matters of dogma even the Catholic Church has not yet attained the fullness of Christ, but can still be perfected from outside. They shall take particular care and shall firmly insist that, in going over the history of the Reformation and the Reformers the defects of Catholics be not so exaggerated and the faults of the Reformers be so dissimulated, or that things which are rather accidental be not so emphasized, that what is most essential, namely the defection from the Catholic faith, be scarcely any longer seen or felt. Finally, they shall take precautions lest, through an excessive and false external activity, or through imprudence and an excited manner of proceeding, the end in view be rather harmed than served.
(The photo is from TIME's magnificent archives)