Justice requires that to lawfully constituted Authority there be given that respect and obedience which is its due; that the laws which are made shall be in wise conformity with the common good; and that, as a matter of conscience all men shall render obedience to these laws.
Pope Pius XIFor them (the peoples of the Soviet Union) We cherish the warmest paternal affection. We are well aware that not a few of them groan beneath the yoke imposed on them by men who in very large part are strangers to the real interests of the country. We recognize that many others were deceived by fallacious hopes. We blame only the system with its authors and abettors who considered Russia the best field for experimenting with a plan elaborated years ago, and who from there continue to spread it from one of the world to the other.
Pope Pius XIThose wretches tainted with the error of Indifferentism and Modernism hold that dogmatic truth is not absolute, but relative: that is, that it must adapt itself to the varying necessities of the times and the varying dispositions of souls, since it is not contained in an unchangeable revelation, but is, by its very nature, meant to accommodate itself to the life of man.
Pope Pius XITo each, therefore, must be given his own share of goods, and the distribution of created goods, which, as every discerning person knows, is laboring today under the gravest evils due to the huge disparity between the few exceedingly rich and the unnumbered propertyless, must be effectively called back to and brought into conformity with the norms of the common good, that is, social justice.
Pope Pius XIIf Socialism, like all errors, contains some truth (which, moreover, the Supreme Pontiffs have never denied), it is based nevertheless on a theory of human society peculiar to itself and irreconcilable with true Christianity. Religious socialism, Christian socialism, are contradictory terms; no one can be at the same time a good Catholic and a true socialist.
Pope Pius XI