Pope Leo XIII
Pope Leo XIII  born Vincenzo Gioacchino Raffaele Luigi Pecci, was Pope from February 20, 1878 to July 20, 1903.
He published many encyclicals, his most widely recognized is titled Rerum Novarum. His Holiness Pope Leo XIII also improved relations with the Eastern Churches.
Rerum Novarum is a splendid defense of the natural right to private property. It is a prophetic denunciation of the evils of socialism and Communism, and against totalitarian control of the means of production by the state, which is often a ploy to grab power and deny human rights. Written in 1891, the truth of its statements are evident in the whole of the tragedies of the 20th century caused by Communism in China and Russia especially are witness. The Pope wrote, "the socialists, working on the poor man's envy of the rich, are striving to do away with private property, and contend that individual possessions should become the common property of all, to be administered by the State or by municipal bodies. They hold that by thus transferring property from private individuals to the community, the present mischievous state of things will be set to rights, inasmuch as each citizen will then get his fair share of whatever there is to enjoy. But their contentions are so clearly powerless to end the controversy that were they carried into effect the working man himself would be among the first to suffer. They are, moreover, emphatically unjust, for they would rob the lawful possessor, distort the functions of the State, and create utter confusion in the community ... The socialists, therefore, in setting aside the parent and setting up a State supervision, act against natural justice, and destroy the structure of the home ... Hence, it is clear that the main tenet of socialism, community of goods, must be utterly rejected, since it only injures those whom it would seem meant to benefit, is directly contrary to the natural rights of mankind, and would introduce confusion and disorder into the commonweal. The first and most fundamental principle, therefore, if one would undertake to alleviate the condition of the masses, must be the inviolability of private property. This being established, we proceed to show where the remedy sought for must be found."
Rerum Novarum also rejects the socialist notion of unrelenting class opposition: "The great mistake made in regard to the matter now under consideration is to take up with the notion that class is naturally hostile to class, and that the wealthy and the working men are intended by nature to live in mutual conflict. So irrational and so false is this view that the direct contrary is the truth. Just as the symmetry of the human frame is the result of the suitable arrangement of the different parts of the body, so in a State is it ordained by nature that these two classes should dwell in harmony and agreement, so as to maintain the balance of the body politic. Each needs the other: capital cannot do without labor, nor labor without capital. Mutual agreement results in the beauty of good order, while perpetual conflict necessarily produces confusion and savage barbarity." Christian teaching counsels and encourages the rich to be kind and merciful to the poor and the poor to rise in society by good work and honest labor. It also demands of employers to strive for just working conditions for all.
Pope Leo XIII wrote about the rights of the Eastern Churches. Pope Leo XIII favored the Eastern Churches preserving their own Tradition: "It has most especially been the habit of the Roman Church, the head of all the Churches, to render to the Churches of the East a great degree of honor and love in remembrance of the Apostles, to rejoice in her turn in their faithful obedience. Amidst changing and difficult times, she has never failed in any way in farsightedness and acts of kindness to sustain them against the forces that would strike them again and again, to hold fast to those that were overwhelmed, to call back those in discord with her. Nor was it the last expression of her watchfulness that she guard and preserve in them whole and entire forever the customs and distinct forms for administering the sacraments that she had declared legitimate in her wise jurisdiction."