15 To arrive at this end, in some places several of these praiseworthy works have called into being an institution of a general character which goes by the name of the "Popular Union." Experience has shown that this has been most effective. The purpose of the Popular Union has been to gather all Catholics, and especially the masses, around a common center of doctrine, propaganda, and social organization. Since, in fact, it answers a need felt in almost every country and its constitution is founded upon the very nature of things, it cannot be said to belong any more to one nation than another, but is suitable to every place where the same needs are present and the same dangers arise. Its extremely popular character causes it to be most desirable and acceptable. It neither disturbs nor hinders the work of existing institutions but, on the contrary, increases their strength and efficiency. Because of its strictly personal organization, it spurs individuals to enter particular institutions, training them to perform practical and useful work, and uniting them all together in one common aim and desire.
Source: Il Fermo Proposito (Vatican.va)