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We are moved by particularly affectionate and benevolent sentiments toward the Catholics of Germany, who are most loyally and obediently devoted to the Apostolic See and accustomed to battle generously and courageously on behalf of the Church. We therefore feel compelled, Venerable Brethren, to devote Our full strength and attention to the discussion of that issue which has arisen among them about workingmen's associations. Concerning this problem several of you, as well as qualified and respected representatives of both viewpoints, have already informed Us repeatedly during the past few years. Conscious of Our Apostolic Office, We have studied this problem most diligently. We fully realize that Our sacred duty is to labor unceasingly that Our beloved sons may preserve the Catholic teaching unadulterated and unimpaired, in no way allowing their Faith to be endangered. If they are not in time urged to be on guard, they would obviously, gradually and inadvertently, fall into the danger of being satisfied with a vague and indefinite form of the Christian religion which has lately been designated as intercredal. This amounts to nothing more than an empty recommendation of a generalized Christianity. Obviously, nothing is more contrary to the teachings of Jesus Christ. Moreover, since Our most ardent desire is the promotion and fortification of concord among Catholics, We constantly try to remove all those occasions of quarrels which dissipate the strength of men of good will and are advantageous only for the enemies of religion. Finally, We desire and intend that the faithful live with their non-Catholic fellow citizens in that peace without which neither the order of human society nor the welfare of the State can endure.

If, however, as We have already said, the existence of this question was known to Us, We nevertheless thought it wise to obtain each of your opinions, Venerable Brethren, before announcing Our decision. You have answered Our questions with that conscientiousness and diligence which the seriousness of the question demands.

http://w2.vatican.va/content/pius-x/en/encyclicals/docuмents/hf_p-x_enc_24091912_singulari-quadam.html

3. These are fundamental principles: No matter what the Christian does, even in the realm of temporal goods, he cannot ignore the supernatural good. Rather, according to the dictates of Christian philosophy, he must order all things to the ultimate end, namely, the Highest Good. All his actions, insofar as they are morally either good or bad (that is to say, whether they agree or disagree with the natural and divine law), are subject to the judgment and judicial office of the Church. All who glory in the name of Christian, either individually or collectively, if they wish to remain true to their vocation, may not foster enmities and dissensions between the classes of civil society. On the contrary, they must promote mutual concord and charity. The social question and its associated controversies, such as the nature and duration of labor, the wages to be paid, and workingmen's strikes, are not simply economic in character. Therefore they cannot be numbered among those which can be settled apart from ecclesiastical authority. "The precise opposite is the truth. It is first of all moral and religious, and for that reason its solution is to be expected mainly from the moral law and the pronouncements of religion."[1]

http://w2.vatican.va/content/pius-x/en/encyclicals/docuмents/hf_p-x_enc_24091912_singulari-quadam.html