On 24th September, 1912, Pope St. Pius X issued his Encyclical Letter Singulari Quadam to the Bishop of Breslau and the other Archbishops and Bishops of Germany on Labor Organizations:
"6. ...The following are the most important of these precautions: In the first place, provision should be made that Catholic workers who are members of the trade unions must also belong to those Catholic associations which are known as "Arbeitervereine." In the event that they must make some sacrifice for this cause, even in a monetary way, We are convinced that they will readily do so for the sake of safeguarding the integrity of their Faith. As has been happily demonstrated, the Catholic workingmen's associations, aided by the clergy and by its leadership and alert direction, are able to achieve very much toward preserving the truths of religion and the purity of morals among their members, and nourish the religious spirit through frequent practices of piety. Therefore, the leaders of such associations, clearly recognizing the needs of the age, are undoubtedly prepared to instruct the workers about their duties in justice and charity, especially regarding all those commandments and precepts in which an accurate knowledge is needed or useful in order to enable them to take an active part in their trade unions according to the principles of Catholic doctrine.
"7. Furthermore, if Catholics are to be permitted to join the trade unions, these associations must avoid everything that is not in accord, either in principle or practice, with the teachings and commandments of the Church or the proper ecclesiastical authorities. Similarly, everything is to be avoided in their literature or public utterances or actions which in the above view would incur censure.
"The Bishops, therefore, should consider it their sacred duty to observe carefully the conduct of all these associations and to watch diligently that the Catholic members do not suffer any harm as a result of their participation. The Catholic members themselves, however, should never permit the unions, whether for the sake of material interests of their members or the union cause as such, to proclaim or support teachings or to engage in activities which would conflict in any way with the directives proclaimed by the supreme teaching authority of the Church, especially those mentioned above. Therefore, as often as problems arise concerning matters of justice or charity, the Bishops should take the greatest care to see that the faithful do not overlook Catholic moral teaching and do not depart from it even a finger's breadth."