Let the storm rage and the sky darken — not for that shall we be dismayed. If we trust as we should in Mary, we shall recognize in her, the Virgin Most Powerful who with virginal foot did crush the head of the serpent.
St. Pope Pius X

2. Accordingly, We first of all declare that all Catholics have a sacred and inviolable duty, both in private and public life, to obey and firmly adhere to and fearlessly profess the principles of Christian truth enunciated by the teaching office of the Catholic Church. In particular We mean those principles which Our Predecessor has most wisely laid down in the encyclical letter Rerum Novarum. We know that the Bishops of Prussia followed these most faithfully in their deliberations at the Fulda Congress of 1900. You yourselves have summarized the fundamental ideas of these principles in your communications regarding this question.

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

One of the last people to actually deserve canonization.

4. Now, concerning workingmen's associations, even though their purpose is to obtain earthly advantages for their members, nonetheless those associations are to be most approved and considered as most useful for the genuine and permanent advantage of their members which are established chiefly on the foundation of the Catholic religion and openly follow the directives of the Church. We have repeated this declaration on several previous occasions in answer to question from various countries. Consequently, such so-called confessional Catholic associations must certainly be established and promoted in every way in Catholic regions as well as in all other districts where it can be presumed that they can sufficiently assist the various needs of their members. However, when there is a question about associations which directly or indirectly touch upon the sphere of religion and morality, it would not be permitted to foster and spread mixed organizations, that is, associations composed of Catholics and non-Catholics, in the areas just mentioned. Over and above other matters, in such organizations there are or certainly can be for our people serious dangers to the integrity of their faith and the due obedience to the commandments and precepts of the Catholic Church. Venerable Brethren, you yourselves have also openly called attention to this question in several of your answers which We have read.

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

6. Not a few of you, Venerable Brethren, have asked Us whether it is permissible to tolerate the so-called Christian Trade Unions that now exist in your dioceses, since, on the one hand, they have a considerably larger number of members than the purely Catholic associations and, on the other hand, if permission were denied serious disadvantages would result. In view of the particular circuмstances of Catholic affairs in Germany, We believe that We should grant this petition. Furthermore, We declare that such mixed associations as now exist within your dioceses can be tolerated and Catholics may be permitted to join them, as long as such toleration does not cease to be appropriate or permissible by reason of new and changed conditions. Necessary precautions, however, must be adopted in order to avoid the dangers which, as has already been mentioned, follow upon such associations.

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

8. We are convinced, Venerable Brethren, that you will diligently take care to see that all these directives of Ours are conscientiously and exactly fulfilled, carefully and constantly reporting to Us concerning this very serious problem. Since We have taken this matter under Our jurisdiction and, after hearing the views of the Bishops, since the decision rests with Us, We hereby command all Catholics of good will to desist from all disputes among themselves concerning this matter. We are confident that with fraternal charity and perfect obedience they will completely and gladly carry out Our command. If any further difficulty arises among them, they should seek its solution in the following manner: Let them first turn to their Bishops for counsel, and then submit the matter to the Apostolic See for its decision.

There is one more point to consider, and it was already implied in what has been said. On the one hand, no one could accuse of bad faith and, under such a pretext, bear ill will toward those who, while firmly defending the teachings and rights of the Church, nonetheless for good reasons have joined or wish to join mixed labor associations in those places where, under certain safeguards, ecclesiastical authority has permitted them in view of local conditions. On the other hand, it would likewise be most reprehensible to oppose or attack the purely Catholic associations (this type of association must, on the contrary, be supported and promoted in every possible manner), and to demand that the so-called intercredal associations be introduced and force their establishment on the grounds that all Catholic associations in every diocese ought to be set up along one and the same pattern.

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

Being greatly moved by the deplorable condition of the Indians in Lower America, our illustrious predecessor Benedict XIV pleaded their cause, as you are aware, in most weighty words, in his letter Immensa Pastorum, given on December 22, 1741; and since we also have to deplore in many places almost the same things that he then lamented, we most earnestly recall those letters of his to your memory. For therein, among other things, Pope Benedict complained that although the Apostolic See had done much, and for a long time, to relieve their afflicted fortunes, there were even the "men of the orthodox faith who, as if they had utterly forgotten all sense of the charity poured forth in our hearts by the Holy Ghost, presumed to reduce the wretched Indians, without the light of faith, and even those who had been washed in the laver of regeneration, to servitude, or to sell them as slaves to others, or to deprive them of their property, and to treat them with such inhumanity that they were thus greatly hindered from embracing the Christian faith, and most strongly moved to regard it with abhorrence." It is true that soon afterwards the worst of these indignities - that is to say, slavery, properly so called - was, by the goodness of the merciful God, abolished; and to this public abolition of slavery in Brazil and in other regions the excellent men who governed those Republics were greatly moved and encouraged by the maternal care and insistence of the Church. And we gladly acknowledge that if it had not been for many and great obstacles that stood in the way, their plans would have had far greater success. Nevertheless, though much has thus been done for the Indians, there is much more that still remains to be done. And, indeed, when we consider the crimes and outrages still committed against them, our heart is filled with horror, and we are moved to great compassion for its most unhappy race. For what can be so cruel and so barbarous as to scourge men and brand them with hot iron, often for most trivial causes, often for a mere lust of cruelty; or, having suddenly overthrown them, to slay hundreds or thousands in one unceasing massacre; or to waste villages and districts and slaughter the inhabitants, so that some tribes, as we understand, have become extinct in these last few years?

http://w2.vatican.va/content/pius-x/en/encyclicals/docuмents/hf_p-x_enc_07061912_lacrimabili-statu.html

3. For our part, indeed, when reports of these things were first brought to us, we hesitated for some time to give credence to such atrocities, since they certainly seemed to be incredible. But after we had been assured by abundant witnesses - to wit, by many of yourselves, Venerable Brethren, by the Delegates of the Apostolic See, by the missioners, and by other men wholly worthy of belief - we can no longer have any doubt as to the truth of these statements.

http://w2.vatican.va/content/pius-x/en/encyclicals/docuмents/hf_p-x_enc_07061912_lacrimabili-statu.html